literature review 5cs

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Chapter 5: The Literature Review

5.4 The Five ‘C’s of Writing a Literature Review

To help you frame and write your literature review, think about these five c’s (Callahan, 2014):

• Cite the material you have referred to and used to help you define the research problem that you will study.
• Compare the various arguments, theories, methods, and findings expressed in the literature.For example, describe where the various researchers agree and where they disagree. Describe the similarities and dissimilarities in approaches to studying related research problems.
• Contrast the various arguments, themes, methods, approaches, and controversies apparent and/or described in the literature. For example, describe what major areas are contested, controversial and/or still in debate.
• Critique the literature. Describe which arguments you find more persuasive and explain why. Explain which approaches, findings, and methods seem most reliable, valid, appropriate, and/or most popular and why. Pay attention to the verbs you use to describe what previous researchers have stated (e.g., asserts, demonstrates, argues, clarifies, etc.).
• Connect the various research studies you reviewed. Describe how your work utilizes, draws upon, departs from, synthesizes, adds to or extends previous research studies.

Research Methods for the Social Sciences: An Introduction Copyright © 2020 by Valerie Sheppard is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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Want to create or adapt books like this? Learn more about how Pressbooks supports open publishing practices.

To help you frame and write your literature review, think about these five c’s (Callahan, 2014):

• Cite the material you have referred to and used to help you define the research problem that you will study.
• Compare the various arguments, theories, methods, and findings expressed in the literature.For example, describe where the various researchers agree and where they disagree. Describe the similarities and dissimilarities in approaches to studying related research problems.
• Contrast the various arguments, themes, methods, approaches, and controversies apparent and/or described in the literature. For example, describe what major areas are contested, controversial and/or still in debate.
• Critique the literature. Describe which arguments you find more persuasive and explain why. Explain which approaches, findings, and methods seem most reliable, valid, appropriate, and/or most popular and why. Pay attention to the verbs you use to describe what previous researchers have stated (e.g., asserts, demonstrates, argues, clarifies, etc.).
• Connect the various research studies you reviewed. Describe how your work utilizes, draws upon, departs from, synthesizes, adds to or extends previous research studies.

Research Methods, Data Collection and Ethics Copyright © 2020 by Valerie Sheppard is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

Share This Book

• Licensing Information
• Contributing Authors
• 1. Let's Get Writing
• 1.1. The 5 C Guidelines
• 1.2. How to Write Articles Quickly and Expertly
• 2. Critical Thinking
• 2.1. Critical Thinking in the Classroom
• 2.2. Necessary and Sufficient Conditions
• 2.3. Good Logic
• 3. APA for Novices
• 3.1. Hoops and Barriers
• 3.2. Crafts and Puzzles
• 3.3. The Papers Trail
• 3.4. The Fine Art of Sentencing
• 3.5. Hurdles
• 3.6. Small Stressors
• 4. Literature Reviews
• 4.1. Introduction to Literature Reviews
• 4.2. What is a Literature Review?
• 4.3. How to Get Started
• 4.4. Where to Find the Literature
• 4.5. Evaluating Sources
• 4.6. Documenting Sources
• 4.7. Synthesizing Sources
• 4.8. Writing the Literature Review
• 4.9. Concluding Thoughts on Literature Reviews
• Technical Tutorials
• Constructing an Annotated Bibliography with Zotero
• Extracting Resource Metadata from a Citation List with AnyStyle.io
• Exporting Zotero to a Spreadsheet
• APA 7 Job Aid
• Index of Topics
• Translations

The 5 C Guidelines

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Producing good academic writing is a difficult skill to master, and writing for an academic audience is different than writing for other audiences.

As an academic writer, you must approach topics differently than you might as a journalist or creative author, and you must emphasize certain skills, such as writing clearly, and ignore other skills that you might have been taught in other contexts, such as using expressive imagery.

To introduce you to this world of academic writing, in this chapter I suggest that you should focus on five hierarchical characteristics of good writing, or the “5 Cs” of good academic writing, which include Clarity, Cogency, Conventionality, Completeness, and Concision. I will now explain each of these in more depth and then discuss tensions between them in writing for different academic audiences.

"Ambiguity is very interesting in writing; it's not very interesting in science." — Janna Levin

Many of us were taught in writing courses that ambiguity and obfuscation of meaning are laudable, because they make our writing seem more complex, deep, and witty. And many of our favorite novelists likely use ambiguity and other tricks to make their writing seem mysterious and complex.

In academic writing, though, these practices simply suggest that you don’t know what you’re talking about. For academics, writing is a way of uncovering truths and realities of the social and physical world, so we should say what we mean. We should make it clear, and say it so that it is impossible for our audience to misunderstand. If your imagined reader ever has to squint her eyes and muse “I wonder what the author really meant by this,” then you have failed. If your imagined reader ever smiles to herself and chuckles at your brilliant wordplay, then you have failed.

This is not to say that academic writing must be joyless and stodgy. It can be witty. It can be deep. But academic depth and wit come from the ideas portrayed through the words, not the words themselves. Too often, writers use ambiguity to hide sloppy thinking and beautiful language to hide destitute ideas. If you say something that could potentially be misunderstood, explain it. If a simpler word will do in place of a more complex one, then use the simple word. Don't be afraid of laying out complex ideas across multiple sentences or paragraphs, but use the space available to you to open up your mind to your reader — what exactly you are thinking, how you are thinking about it, and why.

If you use jargon, technical terms, or initialisms, then you should define or operationalize them. Defining a term means that you are relying upon someone else’s explanation of what the term means and are sticking with it (e.g., “Marwick defines ‘social media’ as…”). Operationalizing a term means that you are using a term that might mean multiple things but you are deciding to only use it in a very finite and specific manner (e.g., “In this paper, I use the word ‘engagement’ to mean…”).

In the case of initialisms, no reader should be expected to know what a PBL, SNS, LMS, CMS, or PBIS is by virtue of the letters themselves, and often even technical initialisms might have multiple meanings (e.g., PBL in education might refer to “project-based learning” or “problem-based learning”). So, when you use initialisms in your writing, define them at the outset (e.g., “positive behavioral interventions and supports (PBIS)”).

If you find yourself repeating the same words over and over again, that’s okay; don’t use variety in your language just for the sake of variety, because in highly technical academic fields every word carries with it technical baggage that you may not intend. If I’m talking about a “curriculum,” then I shouldn’t swap this out with “program,” “module,” “subject,” or “materials” just because I’m tired of saying “curriculum;” each of these words means something very different, and using these terms interchangeably just shows my reader that I don’t understand the differences between them.

In short, other types of writing often rely upon ambiguity and obfuscation to prevent their underlying thought processes from being examined, but examination of these processes is the whole purpose of academic writing. We are not poets, politicians, or preachers, whose primary goals are to be convincing or mystical; rather, we are fellow learners that can only learn together insofar as we can clearly reason together through a dialogic process of clear writing.

"Logic is the beginning of wisdom, not the end." — Leonard Nimoy

Your writing should follow a logical pattern or argument. Arguments generally follow a pattern of identifying one or more assumptions, providing evidence, and drawing a conclusion, such as:

• Assumption - Test creators should design tests to be equitable to all learners who may represent various demographic differences (e.g., race, ethnicity, gender);
• Evidence - Specific research studies show that some prominent tests exhibit inequitable outcomes for students based on race and ethnicity;
• Conclusion - Therefore, test creators should seek to understand why such tests are biased toward some students and should seek to remedy this issue.

Once a conclusion is drawn, it can then be used as an assumption for a subsequent argument. This means that the overarching argument for a paper actually consists of many micro-arguments made throughout the paper that build upon one another like bricks in a wall. Essentially, each paragraph in an academic paper should be treated as its own separate argument, and these arguments then build off of each other to construct the overarching argument.

To help reveal your logical structure, each paragraph should generally represent its own argument. It should start with a topic sentence, provide evidence, and then draw a conclusion that you then build upon in the next paragraph. This is what people often refer to as logical flow: moving from one idea to another without any unsubstantiated gaps.

Since you must substantiate each claim that you make in an academic paper, you should also be careful not to overstate claims (e.g., using superlative language) and not to make claims that you cannot provide evidence for. Oftentimes, this is done by toning down language (e.g., "project-based learning can be an effective pedagogical strategy" [toned down] vs. "project-based learning is the best pedagogical strategy" [superlative]) and using helping verbs, such as may, can, and might (e.g., "social media use may contribute to student depression" vs. "social media make kids depressed"). By toning down your language, you introduce possibilities for doubt (which academics should always be open to) and also prevent your argument from being invalidated by a single counter-instance (e.g., "my kid uses social media and is not depressed, therefore your argument is invalid").

Conventionality

"Writing [without structure] is like playing tennis with the net down." — Robert Frost

In order to understand each other and to know what to expect when we are reading a new manuscript, we need some conventions to provide uniformity. If every article you read had a unique structure, formatting, spacing, capitalization, font size, style, tone, and so forth, you would have increased difficulty comparing it to other work that had gone before.

However, if every time you approach a new piece of writing you know what to expect and where to find it, you will be able to more efficiently recognize where to go and what to look for in the paper. Rather than hunting for the research question, you will know that it will be found right before the methods section and that results will be provided right after that section. Similarly, when you see a bolded and centered line of text, you will know that this means that a new top-level (H1) section is beginning and are not left to wonder why the author made such a bold stylistic choice.

For these reasons, groups of academics have sets of guidelines that they agree to follow, and in our field we follow the American Psychological Association’s (APA) Handbook (version 6).  That handbook covers everything from structure and formatting to style and tone, and theses, dissertations, and class projects require students to follow these same guidelines to help ensure that student work is written in a way that will allow it to be published to a wider audience.

APA Template

To assist you in following APA guidelines, you can access this Google Document that has proper APA heading formats built into it. Then, click on the Styles dropdown > Options and save the APA styles as your default styles, thereby making any new documents that you create in Google Drive follow the APA conventions.

Completeness

"Our duty is to believe that for which we have sufficient evidence, and to suspend our judgment when we have not." — John Lubbock

Since the goal of academic work is to inform as broad an audience as possible and to stand up under the scrutiny of diverse sets of eyes, you must flesh out your writing to address all of the major questions and doubts that your readers might have. Thus, you must not only make an argument that might be convincing to a few people, but you must include sufficient detail and explanation to allow your writing to hold under the scrutiny of the most critical reader. That is, you must write for your greatest critic, not your greatest fan.

This is why academic publishing relies upon peer review. The assumption of peer review is that the best way to ensure quality of writing is to put an author’s work in the hands of dispassionate, unbiased, and diverse experts who typically do not know the identity of the author. This allows reviewers to be honest in their feedback and prevents them from relying upon their personal relationships with or knowledge of the author to fill any gaps (e.g., “I’ve heard of Dr. Avila, and she’s done great work before, so I’m assuming that she did good work here, too”). Rather, every piece of academic writing must stand or fall on its own merits and not on the author’s prior quality of work or reputation.

To do this, you must be explicit and detailed, assume that your reader does not know or trust you as the author, and treat every piece of academic writing as a completely self-contained, self-sustaining, self-validating artifact.

"Brevity is the soul of wit."— William Shakespeare

Most journals in education and other social sciences have strict article word limits of 4,000 to 7,000 words, or roughly 20 to 30 double-spaced pages. This historically has been done to accommodate publishing limitations, because printing pages in a journal is expensive, but even in a digital world, with practically zero publishing costs for adding additional words, imposing limits helps to reduce information overload on readers and to drive more readers to your work.

After all, a moderately-interested reader is much more likely to read a ten-page synopsis of your dissertation than the 200-page document itself, and only the most devoted of readers will stick with it after 20 pages or so. This means that you as the author must not only meet all of the requirements established by the previous guidelines, but you must do it on a strict word budget that avoids unnecessary detail or repetition.

Tensions and Relative Importance

As you’ve probably guessed by this point, the demands of each of these guidelines sometimes conflict with one another. For instance, being complete might mean that you are not very concise, and being clear might reveal the irrationality or poor cogency of your argument. At such times, you must prioritize the guidelines to determine which to emphasize and which to ignore.

Depending on the type of academic writing you are doing, the way that you prioritize guidelines may vary. For instance, a journal article will normally value concision over completeness, due to publishing word limits and trying to make the article as accessible as possible to a wide audience, while a systematic literature review for a thesis or dissertation will do the opposite, requiring students to reveal all of their understanding of their topic and how it is situated within the broader field so that their committees can be assured that they actually know what they are talking about.

Similarly, a quantitative empirical paper will rely heavily upon the conventions established by the paradigm (e.g., p-values, effect sizes), while a qualitative empirical paper will need to provide completeness in its descriptions to allow for trustworthiness and at times ignore conventions. Theoretical papers will also often necessarily defy some conventions in favor of laying out a clear and cogent argument, because the proposed ideas will be new and will not neatly fit within existing reporting approaches but will nonetheless need to be argued in a reasonable and compelling manner.

All this is to say that though these guidelines are all important, their relative importance to one another varies by the context of the writing as determined by purpose, audience, and methods.

Relative Importance of the 5 Cs in Different Settings

By focusing on these 5 Cs and each of their relative importance for your writing context, you can begin to approach your own work in a manner that is systematic and self-reflective. If writing a thesis, for instance, I should start by asking myself "Am I including all pertinent information and details? Is my meaning clear? Is my logic sound? Am I following APA guidelines? And am I careful not to repeat myself or belabor my point?" If writing a theoretical argument for a journal, on the other hand, I should ask myself "Am I within the word limit for the journal? Am I following the journal's stylistic guidelines? Is my argument strong? Is my meaning clear? And do I cover everything that I need to in order to preempt any concerns?"

When asking these questions, something always has to give, such as cutting that explanatory paragraph to get an article under the journal’s required word limit or adding an additional paragraph to make it clear to your thesis readers that you understand the implications of what you’re saying. Through it all, however, each of these guidelines is generally important to follow, and you can only justify ignoring one temporarily in those cases where tensions exist and your intended audience requires you to prioritize another guideline in its place.

Brigham Young University

This content is provided to you freely by BYU Open Learning Network.

Access it online or download it at https://open.byu.edu/rapidwriting/5Cs .

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• How to Write a Literature Review | Guide, Examples, & Templates

How to Write a Literature Review | Guide, Examples, & Templates

Published on January 2, 2023 by Shona McCombes . Revised on September 11, 2023.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic .

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates, and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarize sources—it analyzes, synthesizes , and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

What is the purpose of a literature review, examples of literature reviews, step 1 – search for relevant literature, step 2 – evaluate and select sources, step 3 – identify themes, debates, and gaps, step 4 – outline your literature review’s structure, step 5 – write your literature review, free lecture slides, other interesting articles, frequently asked questions, introduction.

• Quick Run-through
• Step 1 & 2

When you write a thesis , dissertation , or research paper , you will likely have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and its scholarly context
• Develop a theoretical framework and methodology for your research
• Position your work in relation to other researchers and theorists
• Show how your research addresses a gap or contributes to a debate
• Evaluate the current state of research and demonstrate your knowledge of the scholarly debates around your topic.

Writing literature reviews is a particularly important skill if you want to apply for graduate school or pursue a career in research. We’ve written a step-by-step guide that you can follow below.

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See an example

Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research problem and questions .

Make a list of keywords

Start by creating a list of keywords related to your research question. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list as you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some useful databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can also use boolean operators to help narrow down your search.

Make sure to read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

You likely won’t be able to read absolutely everything that has been written on your topic, so it will be necessary to evaluate which sources are most relevant to your research question.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models, and methods?
• Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible , and make sure you read any landmark studies and major theories in your field of research.

You can use our template to summarize and evaluate sources you’re thinking about using. Click on either button below to download.

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It is important to keep track of your sources with citations to avoid plagiarism . It can be helpful to make an annotated bibliography , where you compile full citation information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

To begin organizing your literature review’s argument and structure, be sure you understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly visual platforms like Instagram and Snapchat—this is a gap that you could address in your own research.

There are various approaches to organizing the body of a literature review. Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarizing sources in order.

Try to analyze patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organize your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text , your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, you can follow these tips:

• Summarize and synthesize: give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: don’t just paraphrase other researchers — add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically evaluate: mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: use transition words and topic sentences to draw connections, comparisons and contrasts

In the conclusion, you should summarize the key findings you have taken from the literature and emphasize their significance.

When you’ve finished writing and revising your literature review, don’t forget to proofread thoroughly before submitting. Not a language expert? Check out Scribbr’s professional proofreading services !

This article has been adapted into lecture slides that you can use to teach your students about writing a literature review.

Scribbr slides are free to use, customize, and distribute for educational purposes.

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If you want to know more about the research process , methodology , research bias , or statistics , make sure to check out some of our other articles with explanations and examples.

• Sampling methods
• Simple random sampling
• Stratified sampling
• Cluster sampling
• Likert scales
• Reproducibility

 Statistics

• Null hypothesis
• Statistical power
• Probability distribution
• Effect size
• Poisson distribution

Research bias

• Optimism bias
• Cognitive bias
• Implicit bias
• Hawthorne effect
• Anchoring bias
• Explicit bias

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarize yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

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How To Write A Literature Review - A Complete Guide

Table of Contents

A literature review is much more than just another section in your research paper. It forms the very foundation of your research. It is a formal piece of writing where you analyze the existing theoretical framework, principles, and assumptions and use that as a base to shape your approach to the research question.

Curating and drafting a solid literature review section not only lends more credibility to your research paper but also makes your research tighter and better focused. But, writing literature reviews is a difficult task. It requires extensive reading, plus you have to consider market trends and technological and political changes, which tend to change in the blink of an eye.

Now streamline your literature review process with the help of SciSpace Copilot. With this AI research assistant, you can efficiently synthesize and analyze a vast amount of information, identify key themes and trends, and uncover gaps in the existing research. Get real-time explanations, summaries, and answers to your questions for the paper you're reviewing, making navigating and understanding the complex literature landscape easier.

In this comprehensive guide, we will explore everything from the definition of a literature review, its appropriate length, various types of literature reviews, and how to write one.

What is a literature review?

A literature review is a collation of survey, research, critical evaluation, and assessment of the existing literature in a preferred domain.

Eminent researcher and academic Arlene Fink, in her book Conducting Research Literature Reviews , defines it as the following:

“A literature review surveys books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated.

Literature reviews are designed to provide an overview of sources you have explored while researching a particular topic, and to demonstrate to your readers how your research fits within a larger field of study.”

Simply put, a literature review can be defined as a critical discussion of relevant pre-existing research around your research question and carving out a definitive place for your study in the existing body of knowledge. Literature reviews can be presented in multiple ways: a section of an article, the whole research paper itself, or a chapter of your thesis.

A literature review does function as a summary of sources, but it also allows you to analyze further, interpret, and examine the stated theories, methods, viewpoints, and, of course, the gaps in the existing content.

As an author, you can discuss and interpret the research question and its various aspects and debate your adopted methods to support the claim.

What is the purpose of a literature review?

A literature review is meant to help your readers understand the relevance of your research question and where it fits within the existing body of knowledge. As a researcher, you should use it to set the context, build your argument, and establish the need for your study.

What is the importance of a literature review?

The literature review is a critical part of research papers because it helps you:

• Gain an in-depth understanding of your research question and the surrounding area
• Convey that you have a thorough understanding of your research area and are up-to-date with the latest changes and advancements
• Establish how your research is connected or builds on the existing body of knowledge and how it could contribute to further research
• Elaborate on the validity and suitability of your theoretical framework and research methodology
• Identify and highlight gaps and shortcomings in the existing body of knowledge and how things need to change
• Convey to readers how your study is different or how it contributes to the research area

How long should a literature review be?

Ideally, the literature review should take up 15%-40% of the total length of your manuscript. So, if you have a 10,000-word research paper, the minimum word count could be 1500.

Your literature review format depends heavily on the kind of manuscript you are writing — an entire chapter in case of doctoral theses, a part of the introductory section in a research article, to a full-fledged review article that examines the previously published research on a topic.

Another determining factor is the type of research you are doing. The literature review section tends to be longer for secondary research projects than primary research projects.

What are the different types of literature reviews?

All literature reviews are not the same. There are a variety of possible approaches that you can take. It all depends on the type of research you are pursuing.

Here are the different types of literature reviews:

Argumentative review

It is called an argumentative review when you carefully present literature that only supports or counters a specific argument or premise to establish a viewpoint.

Integrative review

It is a type of literature review focused on building a comprehensive understanding of a topic by combining available theoretical frameworks and empirical evidence.

Methodological review

This approach delves into the ''how'' and the ''what" of the research question —  you cannot look at the outcome in isolation; you should also review the methodology used.

Systematic review

This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research and collect, report, and analyze data from the studies included in the review.

Meta-analysis review

Meta-analysis uses statistical methods to summarize the results of independent studies. By combining information from all relevant studies, meta-analysis can provide more precise estimates of the effects than those derived from the individual studies included within a review.

Historical review

Historical literature reviews focus on examining research throughout a period, often starting with the first time an issue, concept, theory, or phenomenon emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and identify future research's likely directions.

Theoretical Review

This form aims to examine the corpus of theory accumulated regarding an issue, concept, theory, and phenomenon. The theoretical literature review helps to establish what theories exist, the relationships between them, the degree the existing approaches have been investigated, and to develop new hypotheses to be tested.

Scoping Review

The Scoping Review is often used at the beginning of an article, dissertation, or research proposal. It is conducted before the research to highlight gaps in the existing body of knowledge and explains why the project should be greenlit.

State-of-the-Art Review

The State-of-the-Art review is conducted periodically, focusing on the most recent research. It describes what is currently known, understood, or agreed upon regarding the research topic and highlights where there are still disagreements.

Can you use the first person in a literature review?

When writing literature reviews, you should avoid the usage of first-person pronouns. It means that instead of "I argue that" or "we argue that," the appropriate expression would be "this research paper argues that."

Do you need an abstract for a literature review?

Ideally, yes. It is always good to have a condensed summary that is self-contained and independent of the rest of your review. As for how to draft one, you can follow the same fundamental idea when preparing an abstract for a literature review. It should also include:

• The research topic and your motivation behind selecting it
• A one-sentence thesis statement
• An explanation of the kinds of literature featured in the review
• Summary of what you've learned
• Conclusions you drew from the literature you reviewed
• Potential implications and future scope for research

Here's an example of the abstract of a literature review

Is a literature review written in the past tense?

Yes, the literature review should ideally be written in the past tense. You should not use the present or future tense when writing one. The exceptions are when you have statements describing events that happened earlier than the literature you are reviewing or events that are currently occurring; then, you can use the past perfect or present perfect tenses.

How many sources for a literature review?

There are multiple approaches to deciding how many sources to include in a literature review section. The first approach would be to look level you are at as a researcher. For instance, a doctoral thesis might need 60+ sources. In contrast, you might only need to refer to 5-15 sources at the undergraduate level.

The second approach is based on the kind of literature review you are doing — whether it is merely a chapter of your paper or if it is a self-contained paper in itself. When it is just a chapter, sources should equal the total number of pages in your article's body. In the second scenario, you need at least three times as many sources as there are pages in your work.

Quick tips on how to write a literature review

To know how to write a literature review, you must clearly understand its impact and role in establishing your work as substantive research material.

You need to follow the below-mentioned steps, to write a literature review:

• Outline the purpose behind the literature review
• Search relevant literature
• Examine and assess the relevant resources
• Discover connections by drawing deep insights from the resources
• Structure planning to write a good literature review

1. Outline and identify the purpose of  a literature review

As a first step on how to write a literature review, you must know what the research question or topic is and what shape you want your literature review to take. Ensure you understand the research topic inside out, or else seek clarifications. You must be able to the answer below questions before you start:

• How many sources do I need to include?
• What kind of sources should I analyze?
• How much should I critically evaluate each source?
• Should I summarize, synthesize or offer a critique of the sources?
• Do I need to include any background information or definitions?

Additionally, you should know that the narrower your research topic is, the swifter it will be for you to restrict the number of sources to be analyzed.

2. Search relevant literature

Dig deeper into search engines to discover what has already been published around your chosen topic. Make sure you thoroughly go through appropriate reference sources like books, reports, journal articles, government docs, and web-based resources.

You must prepare a list of keywords and their different variations. You can start your search from any library’s catalog, provided you are an active member of that institution. The exact keywords can be extended to widen your research over other databases and academic search engines like:

• Google Scholar
• Microsoft Academic
• Science.gov

Besides, it is not advisable to go through every resource word by word. Alternatively, what you can do is you can start by reading the abstract and then decide whether that source is relevant to your research or not.

Additionally, you must spend surplus time assessing the quality and relevance of resources. It would help if you tried preparing a list of citations to ensure that there lies no repetition of authors, publications, or articles in the literature review.

3. Examine and assess the sources

It is nearly impossible for you to go through every detail in the research article. So rather than trying to fetch every detail, you have to analyze and decide which research sources resemble closest and appear relevant to your chosen domain.

While analyzing the sources, you should look to find out answers to questions like:

• What question or problem has the author been describing and debating?
• What is the definition of critical aspects?
• How well the theories, approach, and methodology have been explained?
• Whether the research theory used some conventional or new innovative approach?
• How relevant are the key findings of the work?
• In what ways does it relate to other sources on the same topic?
• What challenges does this research paper pose to the existing theory
• What are the possible contributions or benefits it adds to the subject domain?

Be always mindful that you refer only to credible and authentic resources. It would be best if you always take references from different publications to validate your theory.

Always keep track of important information or data you can present in your literature review right from the beginning. It will help steer your path from any threats of plagiarism and also make it easier to curate an annotated bibliography or reference section.

4. Discover connections

At this stage, you must start deciding on the argument and structure of your literature review. To accomplish this, you must discover and identify the relations and connections between various resources while drafting your abstract.

A few aspects that you should be aware of while writing a literature review include:

• Rise to prominence: Theories and methods that have gained reputation and supporters over time.
• Constant scrutiny: Concepts or theories that repeatedly went under examination.
• Contradictions and conflicts: Theories, both the supporting and the contradictory ones, for the research topic.
• Knowledge gaps: What exactly does it fail to address, and how to bridge them with further research?
• Influential resources: Significant research projects available that have been upheld as milestones or perhaps, something that can modify the current trends

Once you join the dots between various past research works, it will be easier for you to draw a conclusion and identify your contribution to the existing knowledge base.

5. Structure planning to write a good literature review

There exist different ways towards planning and executing the structure of a literature review. The format of a literature review varies and depends upon the length of the research.

Like any other research paper, the literature review format must contain three sections: introduction, body, and conclusion. The goals and objectives of the research question determine what goes inside these three sections.

Nevertheless, a good literature review can be structured according to the chronological, thematic, methodological, or theoretical framework approach.

Literature review samples

1. Standalone

2. As a section of a research paper

How SciSpace Discover makes literature review a breeze?

SciSpace Discover is a one-stop solution to do an effective literature search and get barrier-free access to scientific knowledge. It is an excellent repository where you can find millions of only peer-reviewed articles and full-text PDF files. Here’s more on how you can use it:

Find the right information

Find what you want quickly and easily with comprehensive search filters that let you narrow down papers according to PDF availability, year of publishing, document type, and affiliated institution. Moreover, you can sort the results based on the publishing date, citation count, and relevance.

Assess credibility of papers quickly

When doing the literature review, it is critical to establish the quality of your sources. They form the foundation of your research. SciSpace Discover helps you assess the quality of a source by providing an overview of its references, citations, and performance metrics.

Get the complete picture in no time

SciSpace Discover’s personalized suggestion engine helps you stay on course and get the complete picture of the topic from one place. Every time you visit an article page, it provides you links to related papers. Besides that, it helps you understand what’s trending, who are the top authors, and who are the leading publishers on a topic.

Make referring sources super easy

To ensure you don't lose track of your sources, you must start noting down your references when doing the literature review. SciSpace Discover makes this step effortless. Click the 'cite' button on an article page, and you will receive preloaded citation text in multiple styles — all you've to do is copy-paste it into your manuscript.

Final tips on how to write a literature review

A massive chunk of time and effort is required to write a good literature review. But, if you go about it systematically, you'll be able to save a ton of time and build a solid foundation for your research.

We hope this guide has helped you answer several key questions you have about writing literature reviews.

Would you like to explore SciSpace Discover and kick off your literature search right away? You can get started here .

Frequently Asked Questions (FAQs)

1. how to start a literature review.

• What questions do you want to answer?

• What sources do you need to answer these questions?

• What information do these sources contain?

• How can you use this information to answer your questions?

2. What to include in a literature review?

• A brief background of the problem or issue

• What has previously been done to address the problem or issue

• A description of what you will do in your project

• How this study will contribute to research on the subject

3. Why literature review is important?

The literature review is an important part of any research project because it allows the writer to look at previous studies on a topic and determine existing gaps in the literature, as well as what has already been done. It will also help them to choose the most appropriate method for their own study.

4. How to cite a literature review in APA format?

To cite a literature review in APA style, you need to provide the author's name, the title of the article, and the year of publication. For example: Patel, A. B., & Stokes, G. S. (2012). The relationship between personality and intelligence: A meta-analysis of longitudinal research. Personality and Individual Differences, 53(1), 16-21

5. What are the components of a literature review?

• A brief introduction to the topic, including its background and context. The introduction should also include a rationale for why the study is being conducted and what it will accomplish.

• A description of the methodologies used in the study. This can include information about data collection methods, sample size, and statistical analyses.

• A presentation of the findings in an organized format that helps readers follow along with the author's conclusions.

6. What are common errors in writing literature review?

• Not spending enough time to critically evaluate the relevance of resources, observations and conclusions.

• Totally relying on secondary data while ignoring primary data.

• Letting your personal bias seep into your interpretation of existing literature.

• No detailed explanation of the procedure to discover and identify an appropriate literature review.

7. What are the 5 C's of writing literature review?

• Cite - the sources you utilized and referenced in your research.

• Compare - existing arguments, hypotheses, methodologies, and conclusions found in the knowledge base.

• Contrast - the arguments, topics, methodologies, approaches, and disputes that may be found in the literature.

• Critique - the literature and describe the ideas and opinions you find more convincing and why.

• Connect - the various studies you reviewed in your research.

8. How many sources should a literature review have?

When it is just a chapter, sources should equal the total number of pages in your article's body. if it is a self-contained paper in itself, you need at least three times as many sources as there are pages in your work.

9. Can literature review have diagrams?

• To represent an abstract idea or concept

• To explain the steps of a process or procedure

• To help readers understand the relationships between different concepts

10. How old should sources be in a literature review?

Sources for a literature review should be as current as possible or not older than ten years. The only exception to this rule is if you are reviewing a historical topic and need to use older sources.

11. What are the types of literature review?

• Argumentative review

• Integrative review

• Methodological review

• Systematic review

• Meta-analysis review

• Historical review

• Theoretical review

• Scoping review

• State-of-the-Art review

12. Is a literature review mandatory?

Yes. Literature review is a mandatory part of any research project. It is a critical step in the process that allows you to establish the scope of your research, and provide a background for the rest of your work.

But before you go,

• Six Online Tools for Easy Literature Review
• Evaluating literature review: systematic vs. scoping reviews
• Systematic Approaches to a Successful Literature Review
• Writing Integrative Literature Reviews: Guidelines and Examples

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Ten Simple Rules for Writing a Literature Review

Marco pautasso.

1 Centre for Functional and Evolutionary Ecology (CEFE), CNRS, Montpellier, France

2 Centre for Biodiversity Synthesis and Analysis (CESAB), FRB, Aix-en-Provence, France

Literature reviews are in great demand in most scientific fields. Their need stems from the ever-increasing output of scientific publications [1] . For example, compared to 1991, in 2008 three, eight, and forty times more papers were indexed in Web of Science on malaria, obesity, and biodiversity, respectively [2] . Given such mountains of papers, scientists cannot be expected to examine in detail every single new paper relevant to their interests [3] . Thus, it is both advantageous and necessary to rely on regular summaries of the recent literature. Although recognition for scientists mainly comes from primary research, timely literature reviews can lead to new synthetic insights and are often widely read [4] . For such summaries to be useful, however, they need to be compiled in a professional way [5] .

When starting from scratch, reviewing the literature can require a titanic amount of work. That is why researchers who have spent their career working on a certain research issue are in a perfect position to review that literature. Some graduate schools are now offering courses in reviewing the literature, given that most research students start their project by producing an overview of what has already been done on their research issue [6] . However, it is likely that most scientists have not thought in detail about how to approach and carry out a literature review.

Reviewing the literature requires the ability to juggle multiple tasks, from finding and evaluating relevant material to synthesising information from various sources, from critical thinking to paraphrasing, evaluating, and citation skills [7] . In this contribution, I share ten simple rules I learned working on about 25 literature reviews as a PhD and postdoctoral student. Ideas and insights also come from discussions with coauthors and colleagues, as well as feedback from reviewers and editors.

Rule 1: Define a Topic and Audience

How to choose which topic to review? There are so many issues in contemporary science that you could spend a lifetime of attending conferences and reading the literature just pondering what to review. On the one hand, if you take several years to choose, several other people may have had the same idea in the meantime. On the other hand, only a well-considered topic is likely to lead to a brilliant literature review [8] . The topic must at least be:

• interesting to you (ideally, you should have come across a series of recent papers related to your line of work that call for a critical summary),
• an important aspect of the field (so that many readers will be interested in the review and there will be enough material to write it), and
• a well-defined issue (otherwise you could potentially include thousands of publications, which would make the review unhelpful).

Ideas for potential reviews may come from papers providing lists of key research questions to be answered [9] , but also from serendipitous moments during desultory reading and discussions. In addition to choosing your topic, you should also select a target audience. In many cases, the topic (e.g., web services in computational biology) will automatically define an audience (e.g., computational biologists), but that same topic may also be of interest to neighbouring fields (e.g., computer science, biology, etc.).

Rule 2: Search and Re-search the Literature

After having chosen your topic and audience, start by checking the literature and downloading relevant papers. Five pieces of advice here:

• keep track of the search items you use (so that your search can be replicated [10] ),
• keep a list of papers whose pdfs you cannot access immediately (so as to retrieve them later with alternative strategies),
• use a paper management system (e.g., Mendeley, Papers, Qiqqa, Sente),
• define early in the process some criteria for exclusion of irrelevant papers (these criteria can then be described in the review to help define its scope), and
• do not just look for research papers in the area you wish to review, but also seek previous reviews.

The chances are high that someone will already have published a literature review ( Figure 1 ), if not exactly on the issue you are planning to tackle, at least on a related topic. If there are already a few or several reviews of the literature on your issue, my advice is not to give up, but to carry on with your own literature review,

The bottom-right situation (many literature reviews but few research papers) is not just a theoretical situation; it applies, for example, to the study of the impacts of climate change on plant diseases, where there appear to be more literature reviews than research studies [33] .

• discussing in your review the approaches, limitations, and conclusions of past reviews,
• trying to find a new angle that has not been covered adequately in the previous reviews, and
• incorporating new material that has inevitably accumulated since their appearance.

When searching the literature for pertinent papers and reviews, the usual rules apply:

• be thorough,
• use different keywords and database sources (e.g., DBLP, Google Scholar, ISI Proceedings, JSTOR Search, Medline, Scopus, Web of Science), and
• look at who has cited past relevant papers and book chapters.

Rule 3: Take Notes While Reading

If you read the papers first, and only afterwards start writing the review, you will need a very good memory to remember who wrote what, and what your impressions and associations were while reading each single paper. My advice is, while reading, to start writing down interesting pieces of information, insights about how to organize the review, and thoughts on what to write. This way, by the time you have read the literature you selected, you will already have a rough draft of the review.

Of course, this draft will still need much rewriting, restructuring, and rethinking to obtain a text with a coherent argument [11] , but you will have avoided the danger posed by staring at a blank document. Be careful when taking notes to use quotation marks if you are provisionally copying verbatim from the literature. It is advisable then to reformulate such quotes with your own words in the final draft. It is important to be careful in noting the references already at this stage, so as to avoid misattributions. Using referencing software from the very beginning of your endeavour will save you time.

Rule 4: Choose the Type of Review You Wish to Write

After having taken notes while reading the literature, you will have a rough idea of the amount of material available for the review. This is probably a good time to decide whether to go for a mini- or a full review. Some journals are now favouring the publication of rather short reviews focusing on the last few years, with a limit on the number of words and citations. A mini-review is not necessarily a minor review: it may well attract more attention from busy readers, although it will inevitably simplify some issues and leave out some relevant material due to space limitations. A full review will have the advantage of more freedom to cover in detail the complexities of a particular scientific development, but may then be left in the pile of the very important papers “to be read” by readers with little time to spare for major monographs.

There is probably a continuum between mini- and full reviews. The same point applies to the dichotomy of descriptive vs. integrative reviews. While descriptive reviews focus on the methodology, findings, and interpretation of each reviewed study, integrative reviews attempt to find common ideas and concepts from the reviewed material [12] . A similar distinction exists between narrative and systematic reviews: while narrative reviews are qualitative, systematic reviews attempt to test a hypothesis based on the published evidence, which is gathered using a predefined protocol to reduce bias [13] , [14] . When systematic reviews analyse quantitative results in a quantitative way, they become meta-analyses. The choice between different review types will have to be made on a case-by-case basis, depending not just on the nature of the material found and the preferences of the target journal(s), but also on the time available to write the review and the number of coauthors [15] .

Rule 5: Keep the Review Focused, but Make It of Broad Interest

Whether your plan is to write a mini- or a full review, it is good advice to keep it focused 16 , 17 . Including material just for the sake of it can easily lead to reviews that are trying to do too many things at once. The need to keep a review focused can be problematic for interdisciplinary reviews, where the aim is to bridge the gap between fields [18] . If you are writing a review on, for example, how epidemiological approaches are used in modelling the spread of ideas, you may be inclined to include material from both parent fields, epidemiology and the study of cultural diffusion. This may be necessary to some extent, but in this case a focused review would only deal in detail with those studies at the interface between epidemiology and the spread of ideas.

While focus is an important feature of a successful review, this requirement has to be balanced with the need to make the review relevant to a broad audience. This square may be circled by discussing the wider implications of the reviewed topic for other disciplines.

Rule 6: Be Critical and Consistent

Reviewing the literature is not stamp collecting. A good review does not just summarize the literature, but discusses it critically, identifies methodological problems, and points out research gaps [19] . After having read a review of the literature, a reader should have a rough idea of:

• the major achievements in the reviewed field,
• the main areas of debate, and
• the outstanding research questions.

It is challenging to achieve a successful review on all these fronts. A solution can be to involve a set of complementary coauthors: some people are excellent at mapping what has been achieved, some others are very good at identifying dark clouds on the horizon, and some have instead a knack at predicting where solutions are going to come from. If your journal club has exactly this sort of team, then you should definitely write a review of the literature! In addition to critical thinking, a literature review needs consistency, for example in the choice of passive vs. active voice and present vs. past tense.

Rule 7: Find a Logical Structure

Like a well-baked cake, a good review has a number of telling features: it is worth the reader's time, timely, systematic, well written, focused, and critical. It also needs a good structure. With reviews, the usual subdivision of research papers into introduction, methods, results, and discussion does not work or is rarely used. However, a general introduction of the context and, toward the end, a recapitulation of the main points covered and take-home messages make sense also in the case of reviews. For systematic reviews, there is a trend towards including information about how the literature was searched (database, keywords, time limits) [20] .

How can you organize the flow of the main body of the review so that the reader will be drawn into and guided through it? It is generally helpful to draw a conceptual scheme of the review, e.g., with mind-mapping techniques. Such diagrams can help recognize a logical way to order and link the various sections of a review [21] . This is the case not just at the writing stage, but also for readers if the diagram is included in the review as a figure. A careful selection of diagrams and figures relevant to the reviewed topic can be very helpful to structure the text too [22] .

Rule 8: Make Use of Feedback

Reviews of the literature are normally peer-reviewed in the same way as research papers, and rightly so [23] . As a rule, incorporating feedback from reviewers greatly helps improve a review draft. Having read the review with a fresh mind, reviewers may spot inaccuracies, inconsistencies, and ambiguities that had not been noticed by the writers due to rereading the typescript too many times. It is however advisable to reread the draft one more time before submission, as a last-minute correction of typos, leaps, and muddled sentences may enable the reviewers to focus on providing advice on the content rather than the form.

Feedback is vital to writing a good review, and should be sought from a variety of colleagues, so as to obtain a diversity of views on the draft. This may lead in some cases to conflicting views on the merits of the paper, and on how to improve it, but such a situation is better than the absence of feedback. A diversity of feedback perspectives on a literature review can help identify where the consensus view stands in the landscape of the current scientific understanding of an issue [24] .

Rule 9: Include Your Own Relevant Research, but Be Objective

In many cases, reviewers of the literature will have published studies relevant to the review they are writing. This could create a conflict of interest: how can reviewers report objectively on their own work [25] ? Some scientists may be overly enthusiastic about what they have published, and thus risk giving too much importance to their own findings in the review. However, bias could also occur in the other direction: some scientists may be unduly dismissive of their own achievements, so that they will tend to downplay their contribution (if any) to a field when reviewing it.

In general, a review of the literature should neither be a public relations brochure nor an exercise in competitive self-denial. If a reviewer is up to the job of producing a well-organized and methodical review, which flows well and provides a service to the readership, then it should be possible to be objective in reviewing one's own relevant findings. In reviews written by multiple authors, this may be achieved by assigning the review of the results of a coauthor to different coauthors.

Rule 10: Be Up-to-Date, but Do Not Forget Older Studies

Given the progressive acceleration in the publication of scientific papers, today's reviews of the literature need awareness not just of the overall direction and achievements of a field of inquiry, but also of the latest studies, so as not to become out-of-date before they have been published. Ideally, a literature review should not identify as a major research gap an issue that has just been addressed in a series of papers in press (the same applies, of course, to older, overlooked studies (“sleeping beauties” [26] )). This implies that literature reviewers would do well to keep an eye on electronic lists of papers in press, given that it can take months before these appear in scientific databases. Some reviews declare that they have scanned the literature up to a certain point in time, but given that peer review can be a rather lengthy process, a full search for newly appeared literature at the revision stage may be worthwhile. Assessing the contribution of papers that have just appeared is particularly challenging, because there is little perspective with which to gauge their significance and impact on further research and society.

Inevitably, new papers on the reviewed topic (including independently written literature reviews) will appear from all quarters after the review has been published, so that there may soon be the need for an updated review. But this is the nature of science [27] – [32] . I wish everybody good luck with writing a review of the literature.

Acknowledgments

Many thanks to M. Barbosa, K. Dehnen-Schmutz, T. Döring, D. Fontaneto, M. Garbelotto, O. Holdenrieder, M. Jeger, D. Lonsdale, A. MacLeod, P. Mills, M. Moslonka-Lefebvre, G. Stancanelli, P. Weisberg, and X. Xu for insights and discussions, and to P. Bourne, T. Matoni, and D. Smith for helpful comments on a previous draft.

Funding Statement

This work was funded by the French Foundation for Research on Biodiversity (FRB) through its Centre for Synthesis and Analysis of Biodiversity data (CESAB), as part of the NETSEED research project. The funders had no role in the preparation of the manuscript.

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Writing a Literature Review

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A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays). When we say “literature review” or refer to “the literature,” we are talking about the research ( scholarship ) in a given field. You will often see the terms “the research,” “the scholarship,” and “the literature” used mostly interchangeably.

Where, when, and why would I write a lit review?

There are a number of different situations where you might write a literature review, each with slightly different expectations; different disciplines, too, have field-specific expectations for what a literature review is and does. For instance, in the humanities, authors might include more overt argumentation and interpretation of source material in their literature reviews, whereas in the sciences, authors are more likely to report study designs and results in their literature reviews; these differences reflect these disciplines’ purposes and conventions in scholarship. You should always look at examples from your own discipline and talk to professors or mentors in your field to be sure you understand your discipline’s conventions, for literature reviews as well as for any other genre.

A literature review can be a part of a research paper or scholarly article, usually falling after the introduction and before the research methods sections. In these cases, the lit review just needs to cover scholarship that is important to the issue you are writing about; sometimes it will also cover key sources that informed your research methodology.

Lit reviews can also be standalone pieces, either as assignments in a class or as publications. In a class, a lit review may be assigned to help students familiarize themselves with a topic and with scholarship in their field, get an idea of the other researchers working on the topic they’re interested in, find gaps in existing research in order to propose new projects, and/or develop a theoretical framework and methodology for later research. As a publication, a lit review usually is meant to help make other scholars’ lives easier by collecting and summarizing, synthesizing, and analyzing existing research on a topic. This can be especially helpful for students or scholars getting into a new research area, or for directing an entire community of scholars toward questions that have not yet been answered.

What are the parts of a lit review?

Most lit reviews use a basic introduction-body-conclusion structure; if your lit review is part of a larger paper, the introduction and conclusion pieces may be just a few sentences while you focus most of your attention on the body. If your lit review is a standalone piece, the introduction and conclusion take up more space and give you a place to discuss your goals, research methods, and conclusions separately from where you discuss the literature itself.

Introduction:

• An introductory paragraph that explains what your working topic and thesis is
• A forecast of key topics or texts that will appear in the review
• Potentially, a description of how you found sources and how you analyzed them for inclusion and discussion in the review (more often found in published, standalone literature reviews than in lit review sections in an article or research paper)
• Summarize and synthesize: Give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: Don’t just paraphrase other researchers – add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically Evaluate: Mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: Use transition words and topic sentence to draw connections, comparisons, and contrasts.

Conclusion:

• Summarize the key findings you have taken from the literature and emphasize their significance
• Connect it back to your primary research question

How should I organize my lit review?

Lit reviews can take many different organizational patterns depending on what you are trying to accomplish with the review. Here are some examples:

• Chronological : The simplest approach is to trace the development of the topic over time, which helps familiarize the audience with the topic (for instance if you are introducing something that is not commonly known in your field). If you choose this strategy, be careful to avoid simply listing and summarizing sources in order. Try to analyze the patterns, turning points, and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred (as mentioned previously, this may not be appropriate in your discipline — check with a teacher or mentor if you’re unsure).
• Thematic : If you have found some recurring central themes that you will continue working with throughout your piece, you can organize your literature review into subsections that address different aspects of the topic. For example, if you are reviewing literature about women and religion, key themes can include the role of women in churches and the religious attitude towards women.
• Qualitative versus quantitative research
• Empirical versus theoretical scholarship
• Divide the research by sociological, historical, or cultural sources
• Theoretical : In many humanities articles, the literature review is the foundation for the theoretical framework. You can use it to discuss various theories, models, and definitions of key concepts. You can argue for the relevance of a specific theoretical approach or combine various theorical concepts to create a framework for your research.

What are some strategies or tips I can use while writing my lit review?

Any lit review is only as good as the research it discusses; make sure your sources are well-chosen and your research is thorough. Don’t be afraid to do more research if you discover a new thread as you’re writing. More info on the research process is available in our "Conducting Research" resources .

As you’re doing your research, create an annotated bibliography ( see our page on the this type of document ). Much of the information used in an annotated bibliography can be used also in a literature review, so you’ll be not only partially drafting your lit review as you research, but also developing your sense of the larger conversation going on among scholars, professionals, and any other stakeholders in your topic.

Usually you will need to synthesize research rather than just summarizing it. This means drawing connections between sources to create a picture of the scholarly conversation on a topic over time. Many student writers struggle to synthesize because they feel they don’t have anything to add to the scholars they are citing; here are some strategies to help you:

• It often helps to remember that the point of these kinds of syntheses is to show your readers how you understand your research, to help them read the rest of your paper.
• Writing teachers often say synthesis is like hosting a dinner party: imagine all your sources are together in a room, discussing your topic. What are they saying to each other?
• Look at the in-text citations in each paragraph. Are you citing just one source for each paragraph? This usually indicates summary only. When you have multiple sources cited in a paragraph, you are more likely to be synthesizing them (not always, but often
• Read more about synthesis here.

The most interesting literature reviews are often written as arguments (again, as mentioned at the beginning of the page, this is discipline-specific and doesn’t work for all situations). Often, the literature review is where you can establish your research as filling a particular gap or as relevant in a particular way. You have some chance to do this in your introduction in an article, but the literature review section gives a more extended opportunity to establish the conversation in the way you would like your readers to see it. You can choose the intellectual lineage you would like to be part of and whose definitions matter most to your thinking (mostly humanities-specific, but this goes for sciences as well). In addressing these points, you argue for your place in the conversation, which tends to make the lit review more compelling than a simple reporting of other sources.

The Ultimate Literature Review Guide

Maybe you are making a research paper, an undergraduate, master's, or doctorate dissertation, a research proposal, a term paper, or a thesis. If this describes you, you need to understand how to write a literature review because it is a critical component within the anatomy of these academic papers.

Usually assigned either as a stand-alone assignment or as part of a bigger assignment, writing a literature review requires keenness. It demands your attention and ability to read, critique, and reason with other authors.

The process of writing a literature review entails the searching and evaluation of available literature in a given subject or relating to your chosen topic. A literature review serves to document what others have said about your chosen topic.

It is not a book by book or article by article summary, neither is it not a descriptive list. Rather, a literature review must be defined by a guiding concept such as a research project, an objective, or essay question.

What is a Literature Review?

A literature review is a piece of academic assignment where the author discusses published information in a given subject area and sometimes information in a given subject area within a certain period of time. It summarizes the synthesis of the concepts, insights, perspectives, and concepts from various sources organized in a specific format. It entails re-organizing, reshuffling, and sifting through the information, interpreting the old information, and combining it to form a new interpretation. A literature review can also trace the intellectual progression of a given field. Finally, it may evaluate the source and advise the readers on the most pertinent and relevant ones.

A literature review shows the readers that you have gathered in-depth knowledge about a given topic and understand where your research fits or adds to the existing body of knowledge.

It demonstrates familiarity with the body of knowledge and establishes your credibility. A literature review also presents a summary of prior research and says how your current project is linked to that research. It also integrates and summarizes the current knowledge about a subject. Finally, it demonstrates that you have acquired knowledge from others, and your research is now a starting point for new ideas. Unlike an argumentative essay, it does not give finality to a topic but instead expounds on a new way of looking at a topic.

A literature review is different from an academic research paper in that, while an academic research paper develops a new argument and likely contains a literature review as its part, a literature review summarizes, synthesizes, and critically analyzes the arguments and ideas of the other scholars or authors without adding new contributions. A literature review for a research paper or any other paper acts as a foundation and support for the new insights that the academic paper contributes.

The Purpose of a Literature Review Paper

You are probably wondering why you need to do a literature review. A literature review can be assigned as part of another assignment or as an independent assignment, just like an annotated bibliography.

A literature review helps you, the author of a research paper, term paper, or thesis, explain why you chose to approach your selected topic from a given perspective. It builds the understanding of the audience/readers concerning a specific topic.

If there is limited time to conduct research, literature reviews also give an overview and act as stepping stones for the research.

In the professional realm, literature reviews are regarded as special reports that update them with the happenstances in their field. For academicians, students, or scholars, the depth and breadth of the literature review proves that one is credible and relevant to their field of study.

In general terms, literature reviews offer a strong background for investigating an issue, topic, or problem. It provides comprehensive knowledge that can be used to answer research questions, pass or refute a hypothesis, and adopt a given lens.

The four major objectives of a literature review include:

• It presents ideas, concepts, and perspectives from literature in an organized way
• It critically analyzes the information gathered through identifying the gaps in current knowledge, showing limitations of theories and perspectives, and formulating areas for further research as well as reviewing the areas of controversy
• It also synthesizes the information in the given literature into a summary
• It surveys the literature in a chosen area of study or one that touches on a given topic.

The Structure of a Literature Review

A literature review is structured like an essay or research paper. It has an introduction, body, and conclusion.

Introduction

The introduction of your literature review should do the following:

• Define the selected topic, provide the context of the literature review, and explain the scope of the literature review. For instance, if you are reviewing the literature on the impacts of COVID-19 on the tourism industry, you can elaborate on the main points emerging from major studies that have looked at the impact of covid on the broader hospitality industry, provide statistics, and then narrow down to the specific sector in the tourism industry that is affected. Do not state what your literature review will not be covering. Instead, focus on what it will be covering.
• Establish the reasons for the literature review
• Explain how the literature review is organized, i.e., the sequence of the literature review

Body Paragraphs

The body paragraphs of the literature review is where you run the show. Each body paragraph should:

• Have a topic sentence that specifies the contents of the paragraph
• Have necessary and relevant pieces of evidence, examples, or illustrations
• Be organized depending on the themes
• Offer insight on the relationship between your selected topic and the subject area
• Move from the general ideas or wider view to the specific focus of your research
• Expose the gap in the literature that your project, research, or study intends to fill
• Examine the past research in the area, highlighting the methodological and theoretical developments, areas of agreements, contentious or controversial areas, and essential studies
• Should be focused on your area or topic of interest
• States how the current work builds or responds to previous studies

Like normal academic papers, the conclusion should wrap up everything. It should:

• Provide a summary of the important points of the existing body of literature
• Establish a gap in the literature that supports the current study
• Evaluate the current state of the literature review
• Outline areas for future studies
• Illustrate how to overcome some of the limitations identified in the literature
• Link the research or study to the existing body of knowledge.

The conclusion summarizes what has emerged from the literature review and reiterates the conclusions.

Organization of Literature Review

You can organize the body of your literature review in different formats. Having a rough idea of the best strategy entirely depends on your choice, the research question, the length, and the scope of your literature review.

You can combine these strategies where necessary, especially if the literature review is longer.  For instance, you can adopt a thematic approach for your overall structure but take a chronological approach in discussing the themes.

Let's explore the various organizational strategies you can use when writing a literature review.

Chronological

A literature review organized through the chronological approach entails writing about the materials depending on when they were published.

The chronological approach is the simplest to adopt when tracing the development of a topic through time.

If you select this strategy, be ready to avoid listing and summarizing the sources in order as we do with annotated bibliography . Instead, summarize, synthesize, and compare and contrast ideas, turning points, points of view, and major debates that shape the direction of the field you are interested in. You should also present your interpretation of how and why some developments occurred.

By publication

When writing a literature review, you can also organize it using their publication chronology.

You can organize a literature review by trend. This way, you end up with sections that detail the eras within the specific periods when the change was noticed.

Thematic literature reviews are organized around a given topic, issue, or theme. This approach is excellent if you have identified recurring central themes and need to organize your literature review based on the themes. Doing so helps in streamlining ideas that relate to different aspects of the topic.

For instance, if you are reviewing the literature on childhood obesity, you can talk about nutrition, physical activity, genetics, advertising, social status, and other aspects related to childhood obesity.

Methodological

When you write a literature review with the methodological approach, your chief focus is on the methods of the researchers who conducted primary studies. In addition, you can look at the types of data collection methods (qualitative, quantitative, or mixed methods), sampling strategies, samples, data collection tools, and other aspects related to methodology.

It is best to explore how the topic has been developed through empirical and theoretical scholarship. You can as well categorize and classify the literature based on subject, points-of-view, and findings.

Theoretical

You can also arrange the body paragraphs of your literature based on the theoretical constructs, frameworks, or foundations of the past studies. Look at the theories, models, definitions, and frameworks that guided the studies.

For instance, if it's a leadership paper, check on leadership theories such as transactional, transformational, situational, contingency, and charismatic leadership theory. You can also look at the types of leadership or followership.

You need to argue for or against the relevance of a specific theoretical approach or combine different theoretical approaches to create a framework that guides your current research.

The 5Cs of a Literature Review

Given that a literature review is dense with information, the work must be intelligibly structured to allow easier readership, grasp the key concepts, and appreciate the purpose of a literature review. To achieve that, it is imperative to integrate the 5Cs (cite, compare, contrast, critique, and connect) into your literature review.

• Cite: The literature review must primarily focus on literature relevant to a given subject area or topic. The material or sources that you refer to and use should define the research problem you are studying.
• Compare: Your literature review must compare various arguments, methods, theories, findings, and approaches expressed in different literature. Describe how different researchers agree and disagree on issues and the similarities and dissimilarities of the approaches to studying related research issues.
• Contract: When writing your literature review, contrast the various arguments, themes, methodologies, approaches, and controversies expressed in literature. For instance, what are the major areas of disagreement or debate?
• Critique: As you write your literature review, remember to describe the arguments you find persuasive and explain the reasons for the same. Explain the approaches, methods, and findings that you deem reliable, relevant, and valid, and explain why. You also need to pay close attention to the verbs you use when describing the facts stated, asserted, expressed, argued, clarified by the previous researchers. Your literature review must be critical, more than just a summary of what others said. It should criticize the assumptions, values, and beliefs that influence the thoughts of the authors.
• Connect: Your literature review must also connect the various research studies that you have reviewed. Describe how the work uses, draws from, departs from, synthesizes, adds, or extrapolates the previous research studies. Connecting ideas in a literature review help to make it convincing as it enables you to gather and analyze facts better. It also becomes contributive in that it gathers the most relevant information to support research where there is none. Finally, it extends the current knowledge, theory, and point of view.

Above all, a good literature review has to be clear, concise, convincing, contributive, and critical.

The Six Proven and Tested Steps for Writing a Literature Review

Now that we understand the various aspects of a literature review let's look at the core steps that one takes when writing one. Follow these steps to write an excellent literature review without a struggle.

First Step: Conduct a comprehensive literature search

Before writing a literature review, you need to find out what other scholars have presented or published about your subject, field, or chosen topic. To do so, you need to conduct a comprehensive literature search. It is the first step when writing a literature review, and there are different strategies to do so.

Naturally, the first step for your literature review writing process entails scavenging for the existing research that is relevant to your topic. This step is standard whether you are writing a literature review for a proposal, dissertation, or literature review section for a research or term paper assignment.

However, if you are doing the literature review as an independent assignment, you must choose your focus and develop a central question that will direct your search. That is the question that enables you to collect good data. It is that question that you must answer through your literature review.

To conduct a good search, follow these tips:

1.      Define all the key terms

Begin by defining the research project or topic. And if you have a question, ensure that you internalize it at this point. Next, ask yourself the major concepts you need to feature in your literature review and compile a list of these keywords, related terms, and synonyms. These will be your seed keywords when developing a research strategy.

2.      Search for relevant sources

Using the keywords, you then begin searching for sources. There are various tricks and tips that you can use to get as many sources as possible then narrow down to the best. Here is where you put on the cap of a hunter, a researcher, or a scavenger. Here are some tips:

• Search through Google's academic search engine, Google Scholar for high-level journal articles, PDF publications, and studies that match your keywords. It is a free-to-access feature that every student uses to get quality articles.
• Use the university database to access the articles from the internet that required paying to access. For instance, an article on Google Scholar might redirect you to another databases whose access is paid for; your school database can help you download the article without having to pay.
• Snowballing from your journal articles can also be a great move. For instance, after reading a journal article and seeing that it fits your topic or research context, check its reference list section and select the relevant ones. Then, search them online and from the school database.
• You can also scavenge through dissertations from ProQuest, Stanford SearchWorks, EBSCO, and Open Access Theses & Dissertations, to find sources that address your research topic. Finally, skim through the literature review section of the dissertation chapters and identify, extract, and store relevant literature sources. When selecting the sources, only choose peer-reviewed articles published within the last five years unless you are talking about seminal works.

Some other potential sources for your literature review apart from the library catalog of your university include INSPEC, Project Muse, Medline, EconLit, and JSTOR. Do not limit yourself; even the articles found on Science Direct can be good as long as they meet the criteria you have identified for your literature review. You can also check publisher websites, newspapers and magazines, conference papers, government publications, bulletins, and periodicals.

When searching for literature review, you can use Boolean operators to narrow your search and identify good sources. For example, you can use AND find sources that also contain more than one keyword, OR find the sources that contain a synonym of your keyword, and NOT exclude the results that contain certain unwanted terms.

You can select the articles to keep by reading the abstracts then judging whether they are fit for your question or work. If you have authors who are prominently cited in many sources, they are an authority, check out whether there are pieces of their work that can match your inclusion criteria.

Second Step: Organize, Clean, and Synthesize the sources

Assuming that you have your list of articles at this point, it is time to now clean out the bad and remain with what matters. You need to evaluate the sources further to determine if they are fit for entry into your literature review.

You need to begin by logging the reference information. For this, you can use online citation management tools such as Mendeley or Zotero. You are better of with these reference managers, and if you are patient enough, you can also use the MS Word Inbuilt reference manager. Keeping track of citations is necessary to avoid plagiarism. Besides, if you are to write an annotated bibliography or fill a literature evaluation table, it would be straightforward. Be sure to choose the appropriate citation style: MLA, APA, Harvard, Chicago/Turabian, or Oxford styles.

You can then further profile the contents of the articles based on major arguments, context, date, author, title, methodology, quotations, and notes. Of course, this means that you need to read every source and drop those that are not really reliable, credible, and relevant.

It would help if you took notes as you read the articles. These notes are beneficial once you begin writing. As a matter of fact, you can use an excel sheet to document different aspects of these sources.

If you want to synthesize the articles sufficiently, have an excel sheet with these columns:

• Author and publication information - write all the publisher, author, and publication details of the article.
• Keywords – list the keywords, concepts, vocabulary, or themes that recur in the article.
• Arguments – write the major arguments, points, or issues an article focuses on
• Context – list the context of the article: socio-economic, political, spiritual, etc
• Methodology – the data research methods used
• Quotes – the most outstanding quotes from the source
• Notes – any special notes about the source. For instance, how it supports your research or question.

After detailing the components of the articles, it is now time to synthesize the information. You can create mind maps, concept maps, or relationship diagrams. Here are some important questions to ask yourself:

• What problem is the author addressing?
• What major concepts stand out, and how does an author define them?
• What are the major themes, theories, methods, and models used?
• Is the research based on an established framework or foundation?
• What are the findings of the study?
• What are the limitations and strengths of the study?
• Does the research relate to other pieces of literature? How?
• How does the chosen research contribute to your topic or area of interest?
• What gaps are there in the current research?
• What further areas of research do the authors recommend, and is your research addressing these areas?

Third Step: Organizing facts for your review

Now that you know what the authors have argued or said, you need to organize the arguments of your literature review and determine the appropriate structure to use. Check whether there are links between sources you read and borrow ideas from your notes; identify the themes, debates, and gaps.

You can identify the trends and patterns in results, methodology, and theory over time and check the themes that recur in the literature. Also, check the debates, contradictions, and conflicts between authors on subjects. Next, list the pivotal publications or the seminal works that highlight landmark studies that developed theories or changed the direction of a given field. Finally, check if there is a missing link in the literature and weaknesses that must be addressed.

Doing the above step helps you contextualize your literature review. It also allows you to choose an appropriate approach to your literature review and show how your research addresses the deficiencies in past research and contributes to knowledge in the field.

Fourth Step: Choose an appropriate Structure and write an outline

As we explored earlier, there are different approaches. Whether you go for chronological, thematic, theoretical, methodological, trend, or publication, you need to have an introduction, body, and conclusion.

Write an outline of your literature review, which is more of a blueprint that will guide your writing process. A detailed outline is a skeleton that helps you to envision how the piece of academic task would be. It enables you to avoid writing then realizing you omitted or overdid a section.

Although you will most likely derail off your structure, it is best to have it so that you can trace where you are when writing. It also eliminates the wastage of word count on things that do not matter.

Allocate the most optimum word count limits for every section of your literature review based on their relevance to the overall structure.

Fifth Step: Write your Literature Review

Now that you have the blueprint – your detailed literature review outline, write up the paper confidently. The only barrier here can be writer's block and procrastination. Try to avoid these two barriers and work early enough to avoid the pressure of writing a literature review in a rush.

The first draft is just that, a draft with so many mistakes. So, write first, then edit later. Then, express your thoughts, arrange and rearrange them, refine the points, and focus on perfection later.

With the initial draft written, take a break for as long as time allows, minding the deadline so that you can develop an objective and fresh mind for revision.

Sixth Step: Revise, Edit, and Polish

Now that you have done what most people find challenging, you need to polish it to achieve the 100% mark. You can polish your literature review by sending it to the supervisor for criticism and comments. When you receive the feedback, you can then edit the paper.

Alternatively, share the draft with a colleague or editor and ask if they understand what you wrote. If you want a peer-to-peer editing program, you can use our online editing service. We have strict and experienced academic editors. These research specialists can come in handy when polishing your literature review. Remember, maintaining simplicity when writing your literature review matters more.

After all, is done, check your grammar, punctuation, language use, verbs, tenses, nouns, and formatting to ensure that you are all set, then submit for grading.

Tips and Tricks for Writing and Outstanding Literature Review

Here are a few tips and tricks from our literature review writers to help you finish your literature review assignment. These tips and tricks have been tried, tested, and proven to work. They can be your guiding principles when writing your literature review.

• Ensure that your literature review includes many primary data sources. Unfortunately, this is where most students err. Don't fall into the temptation of using secondary sources for their availability. Primary resources are the best for literature reviews.
• Describe the procedures used to identify the sources that you included in the literature review.
• Ensure that your literature review is not just a summary of sources; synthesize the contents of these sources.
• Connect ideas from different resources for coherent, clear, concise, and fitting analysis
• Ensure that your lit review is grammatically correct
• Check all the spelling and punctuation errors
• Never use first-person "I" or "you" in your literature review
• Plan and start writing your literature review later
• Stick to one academic formatting style
• Do not use descriptive and narrative approaches, be critical as well
• Evaluate the opposing opinions and draw conclusions
• Use quotes sparingly when writing
• Be selective with the information you extract from the source
• Use evidence to support facts and ideas
• Keep and maintain your own voice when writing
• Use caution when paraphrasing
• Revise and polish before submitting.
• Have works cited, references, or bibliography section
• Use headings and subheadings if necessary
• When choosing the sources, focus on relevance, authority, and currency.
• Evaluate the literature rather than just summarize it
• Connect the ideas in the literature to your research
• If it is a literature review for a research project, include the theoretical discussion about the selected methodology and argue why the research is necessary
• Compare and contrast the sources to each other instead of writing discrete sections for each source

Literature review checklist

• Did you outline the scope and purpose of the review?
• Have you identified appropriate source material mainly from primary and secondary sources?
• Have you written a draft and edited it carefully?
• Is your literature review submitted on time and in the correct format?
• Are the tenses correct?
• Have you appropriately placed the punctuations?
• Are the sources used listed at the end?
• Did you keep bibliographical records of all the researched material?
• Is each source critically reviewed?
• Have you organized all the material you obtained from the sources?
• Have you developed your approach?
• Are the sources used current, relevant, authoritative, appropriate, and purposeful?
• Is the literature review based on current literature?
• Does your literature review fill the gap in knowledge and literature?
• Does the literature review have balanced paragraphs?

We wish you the best of luck as you write your literature review; you will need it!

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What is a Literature Review? How to Write It (with Examples)

A literature review is a critical analysis and synthesis of existing research on a particular topic. It provides an overview of the current state of knowledge, identifies gaps, and highlights key findings in the literature. 1 The purpose of a literature review is to situate your own research within the context of existing scholarship, demonstrating your understanding of the topic and showing how your work contributes to the ongoing conversation in the field. Learning how to write a literature review is a critical tool for successful research. Your ability to summarize and synthesize prior research pertaining to a certain topic demonstrates your grasp on the topic of study, and assists in the learning process. 

Table of Contents

• What is the purpose of literature review? 
• a. Habitat Loss and Species Extinction: 
• b. Range Shifts and Phenological Changes: 
• c. Ocean Acidification and Coral Reefs: 
• d. Adaptive Strategies and Conservation Efforts: 

How to write a good literature review 

• Choose a Topic and Define the Research Question: 
• Decide on the Scope of Your Review: 
• Select Databases for Searches: 
• Conduct Searches and Keep Track: 
• Review the Literature: 
• Organize and Write Your Literature Review: 
• How to write a literature review faster with Paperpal? 
• Frequently asked questions 

What is a literature review?

A well-conducted literature review demonstrates the researcher’s familiarity with the existing literature, establishes the context for their own research, and contributes to scholarly conversations on the topic. One of the purposes of a literature review is also to help researchers avoid duplicating previous work and ensure that their research is informed by and builds upon the existing body of knowledge.

What is the purpose of literature review?

A literature review serves several important purposes within academic and research contexts. Here are some key objectives and functions of a literature review: 2  

1. Contextualizing the Research Problem: The literature review provides a background and context for the research problem under investigation. It helps to situate the study within the existing body of knowledge. 

2. Identifying Gaps in Knowledge: By identifying gaps, contradictions, or areas requiring further research, the researcher can shape the research question and justify the significance of the study. This is crucial for ensuring that the new research contributes something novel to the field. 

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3. Understanding Theoretical and Conceptual Frameworks: Literature reviews help researchers gain an understanding of the theoretical and conceptual frameworks used in previous studies. This aids in the development of a theoretical framework for the current research. 

4. Providing Methodological Insights: Another purpose of literature reviews is that it allows researchers to learn about the methodologies employed in previous studies. This can help in choosing appropriate research methods for the current study and avoiding pitfalls that others may have encountered. 

5. Establishing Credibility: A well-conducted literature review demonstrates the researcher’s familiarity with existing scholarship, establishing their credibility and expertise in the field. It also helps in building a solid foundation for the new research. 

6. Informing Hypotheses or Research Questions: The literature review guides the formulation of hypotheses or research questions by highlighting relevant findings and areas of uncertainty in existing literature. 

Literature review example

Let’s delve deeper with a literature review example: Let’s say your literature review is about the impact of climate change on biodiversity. You might format your literature review into sections such as the effects of climate change on habitat loss and species extinction, phenological changes, and marine biodiversity. Each section would then summarize and analyze relevant studies in those areas, highlighting key findings and identifying gaps in the research. The review would conclude by emphasizing the need for further research on specific aspects of the relationship between climate change and biodiversity. The following literature review template provides a glimpse into the recommended literature review structure and content, demonstrating how research findings are organized around specific themes within a broader topic. 

Literature Review on Climate Change Impacts on Biodiversity:

Climate change is a global phenomenon with far-reaching consequences, including significant impacts on biodiversity. This literature review synthesizes key findings from various studies: 

a. Habitat Loss and Species Extinction:

Climate change-induced alterations in temperature and precipitation patterns contribute to habitat loss, affecting numerous species (Thomas et al., 2004). The review discusses how these changes increase the risk of extinction, particularly for species with specific habitat requirements. 

b. Range Shifts and Phenological Changes:

Observations of range shifts and changes in the timing of biological events (phenology) are documented in response to changing climatic conditions (Parmesan & Yohe, 2003). These shifts affect ecosystems and may lead to mismatches between species and their resources. 

c. Ocean Acidification and Coral Reefs:

The review explores the impact of climate change on marine biodiversity, emphasizing ocean acidification’s threat to coral reefs (Hoegh-Guldberg et al., 2007). Changes in pH levels negatively affect coral calcification, disrupting the delicate balance of marine ecosystems. 

d. Adaptive Strategies and Conservation Efforts:

Recognizing the urgency of the situation, the literature review discusses various adaptive strategies adopted by species and conservation efforts aimed at mitigating the impacts of climate change on biodiversity (Hannah et al., 2007). It emphasizes the importance of interdisciplinary approaches for effective conservation planning. 

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Writing a literature review involves summarizing and synthesizing existing research on a particular topic. A good literature review format should include the following elements. 

Introduction: The introduction sets the stage for your literature review, providing context and introducing the main focus of your review. 

• Opening Statement: Begin with a general statement about the broader topic and its significance in the field. 
• Scope and Purpose: Clearly define the scope of your literature review. Explain the specific research question or objective you aim to address. 
• Organizational Framework: Briefly outline the structure of your literature review, indicating how you will categorize and discuss the existing research. 
• Significance of the Study: Highlight why your literature review is important and how it contributes to the understanding of the chosen topic. 
• Thesis Statement: Conclude the introduction with a concise thesis statement that outlines the main argument or perspective you will develop in the body of the literature review. 

Body: The body of the literature review is where you provide a comprehensive analysis of existing literature, grouping studies based on themes, methodologies, or other relevant criteria. 

• Organize by Theme or Concept: Group studies that share common themes, concepts, or methodologies. Discuss each theme or concept in detail, summarizing key findings and identifying gaps or areas of disagreement. 
• Critical Analysis: Evaluate the strengths and weaknesses of each study. Discuss the methodologies used, the quality of evidence, and the overall contribution of each work to the understanding of the topic. 
• Synthesis of Findings: Synthesize the information from different studies to highlight trends, patterns, or areas of consensus in the literature. 
• Identification of Gaps: Discuss any gaps or limitations in the existing research and explain how your review contributes to filling these gaps. 
• Transition between Sections: Provide smooth transitions between different themes or concepts to maintain the flow of your literature review. 

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Conclusion: The conclusion of your literature review should summarize the main findings, highlight the contributions of the review, and suggest avenues for future research. 

• Summary of Key Findings: Recap the main findings from the literature and restate how they contribute to your research question or objective. 
• Contributions to the Field: Discuss the overall contribution of your literature review to the existing knowledge in the field. 
• Implications and Applications: Explore the practical implications of the findings and suggest how they might impact future research or practice. 
• Recommendations for Future Research: Identify areas that require further investigation and propose potential directions for future research in the field. 
• Final Thoughts: Conclude with a final reflection on the importance of your literature review and its relevance to the broader academic community. 

Conducting a literature review

Conducting a literature review is an essential step in research that involves reviewing and analyzing existing literature on a specific topic. It’s important to know how to do a literature review effectively, so here are the steps to follow: 1  

Choose a Topic and Define the Research Question:

• Select a topic that is relevant to your field of study. 
• Clearly define your research question or objective. Determine what specific aspect of the topic do you want to explore? 

Decide on the Scope of Your Review:

• Determine the timeframe for your literature review. Are you focusing on recent developments, or do you want a historical overview? 
• Consider the geographical scope. Is your review global, or are you focusing on a specific region? 
• Define the inclusion and exclusion criteria. What types of sources will you include? Are there specific types of studies or publications you will exclude? 

Select Databases for Searches:

• Identify relevant databases for your field. Examples include PubMed, IEEE Xplore, Scopus, Web of Science, and Google Scholar. 
• Consider searching in library catalogs, institutional repositories, and specialized databases related to your topic. 

Conduct Searches and Keep Track:

• Develop a systematic search strategy using keywords, Boolean operators (AND, OR, NOT), and other search techniques. 
• Record and document your search strategy for transparency and replicability. 
• Keep track of the articles, including publication details, abstracts, and links. Use citation management tools like EndNote, Zotero, or Mendeley to organize your references. 

Review the Literature:

• Evaluate the relevance and quality of each source. Consider the methodology, sample size, and results of studies. 
• Organize the literature by themes or key concepts. Identify patterns, trends, and gaps in the existing research. 
• Summarize key findings and arguments from each source. Compare and contrast different perspectives. 
• Identify areas where there is a consensus in the literature and where there are conflicting opinions. 
• Provide critical analysis and synthesis of the literature. What are the strengths and weaknesses of existing research? 

Organize and Write Your Literature Review:

• Literature review outline should be based on themes, chronological order, or methodological approaches. 
• Write a clear and coherent narrative that synthesizes the information gathered. 
• Use proper citations for each source and ensure consistency in your citation style (APA, MLA, Chicago, etc.). 
• Conclude your literature review by summarizing key findings, identifying gaps, and suggesting areas for future research. 

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• Ask a question: Get started with a new document on paperpal.com. Click on the “Research” feature and type your question in plain English. Paperpal will scour over 250 million research articles, including conference papers and preprints, to provide you with accurate insights and citations. 
• Review and Save: Paperpal summarizes the information, while citing sources and listing relevant reads. You can quickly scan the results to identify relevant references and save these directly to your built-in citations library for later access. 
• Cite with Confidence: Paperpal makes it easy to incorporate relevant citations and references into your writing, ensuring your arguments are well-supported by credible sources. This translates to a polished, well-researched literature review. 

The literature review sample and detailed advice on writing and conducting a review will help you produce a well-structured report. But remember that a good literature review is an ongoing process, and it may be necessary to revisit and update it as your research progresses. By combining effortless research with an easy citation process, Paperpal Research streamlines the literature review process and empowers you to write faster and with more confidence. Try Paperpal Research now and see for yourself.  

Frequently asked questions

A literature review is a critical and comprehensive analysis of existing literature (published and unpublished works) on a specific topic or research question and provides a synthesis of the current state of knowledge in a particular field. A well-conducted literature review is crucial for researchers to build upon existing knowledge, avoid duplication of efforts, and contribute to the advancement of their field. It also helps researchers situate their work within a broader context and facilitates the development of a sound theoretical and conceptual framework for their studies.

Literature review is a crucial component of research writing, providing a solid background for a research paper’s investigation. The aim is to keep professionals up to date by providing an understanding of ongoing developments within a specific field, including research methods, and experimental techniques used in that field, and present that knowledge in the form of a written report. Also, the depth and breadth of the literature review emphasizes the credibility of the scholar in his or her field.  

Before writing a literature review, it’s essential to undertake several preparatory steps to ensure that your review is well-researched, organized, and focused. This includes choosing a topic of general interest to you and doing exploratory research on that topic, writing an annotated bibliography, and noting major points, especially those that relate to the position you have taken on the topic. 

Literature reviews and academic research papers are essential components of scholarly work but serve different purposes within the academic realm. 3 A literature review aims to provide a foundation for understanding the current state of research on a particular topic, identify gaps or controversies, and lay the groundwork for future research. Therefore, it draws heavily from existing academic sources, including books, journal articles, and other scholarly publications. In contrast, an academic research paper aims to present new knowledge, contribute to the academic discourse, and advance the understanding of a specific research question. Therefore, it involves a mix of existing literature (in the introduction and literature review sections) and original data or findings obtained through research methods. 

Literature reviews are essential components of academic and research papers, and various strategies can be employed to conduct them effectively. If you want to know how to write a literature review for a research paper, here are four common approaches that are often used by researchers.  Chronological Review: This strategy involves organizing the literature based on the chronological order of publication. It helps to trace the development of a topic over time, showing how ideas, theories, and research have evolved.  Thematic Review: Thematic reviews focus on identifying and analyzing themes or topics that cut across different studies. Instead of organizing the literature chronologically, it is grouped by key themes or concepts, allowing for a comprehensive exploration of various aspects of the topic.  Methodological Review: This strategy involves organizing the literature based on the research methods employed in different studies. It helps to highlight the strengths and weaknesses of various methodologies and allows the reader to evaluate the reliability and validity of the research findings.  Theoretical Review: A theoretical review examines the literature based on the theoretical frameworks used in different studies. This approach helps to identify the key theories that have been applied to the topic and assess their contributions to the understanding of the subject.  It’s important to note that these strategies are not mutually exclusive, and a literature review may combine elements of more than one approach. The choice of strategy depends on the research question, the nature of the literature available, and the goals of the review. Additionally, other strategies, such as integrative reviews or systematic reviews, may be employed depending on the specific requirements of the research.

The literature review format can vary depending on the specific publication guidelines. However, there are some common elements and structures that are often followed. Here is a general guideline for the format of a literature review:  Introduction:   Provide an overview of the topic.  Define the scope and purpose of the literature review.  State the research question or objective.  Body:   Organize the literature by themes, concepts, or chronology.  Critically analyze and evaluate each source.  Discuss the strengths and weaknesses of the studies.  Highlight any methodological limitations or biases.  Identify patterns, connections, or contradictions in the existing research.  Conclusion:   Summarize the key points discussed in the literature review.  Highlight the research gap.  Address the research question or objective stated in the introduction.  Highlight the contributions of the review and suggest directions for future research.

Both annotated bibliographies and literature reviews involve the examination of scholarly sources. While annotated bibliographies focus on individual sources with brief annotations, literature reviews provide a more in-depth, integrated, and comprehensive analysis of existing literature on a specific topic. The key differences are as follows: 

References 

• Denney, A. S., & Tewksbury, R. (2013). How to write a literature review.  Journal of criminal justice education ,  24 (2), 218-234. 
• Pan, M. L. (2016).  Preparing literature reviews: Qualitative and quantitative approaches . Taylor & Francis. 
• Cantero, C. (2019). How to write a literature review.  San José State University Writing Center . 

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What is a literature review? [with examples]

What is a literature review?

The purpose of a literature review, how to write a literature review, the format of a literature review, general formatting rules, the length of a literature review, literature review examples, frequently asked questions about literature reviews, related articles.

A literature review is an assessment of the sources in a chosen topic of research.

In a literature review, you’re expected to report on the existing scholarly conversation, without adding new contributions.

If you are currently writing one, you've come to the right place. In the following paragraphs, we will explain:

• the objective of a literature review
• how to write a literature review
• the basic format of a literature review

Tip: It’s not always mandatory to add a literature review in a paper. Theses and dissertations often include them, whereas research papers may not. Make sure to consult with your instructor for exact requirements.

The four main objectives of a literature review are:

• Studying the references of your research area
• Summarizing the main arguments
• Identifying current gaps, stances, and issues
• Presenting all of the above in a text

Ultimately, the main goal of a literature review is to provide the researcher with sufficient knowledge about the topic in question so that they can eventually make an intervention.

The format of a literature review is fairly standard. It includes an:

• introduction that briefly introduces the main topic
• body that includes the main discussion of the key arguments
• conclusion that highlights the gaps and issues of the literature

➡️ Take a look at our guide on how to write a literature review to learn more about how to structure a literature review.

First of all, a literature review should have its own labeled section. You should indicate clearly in the table of contents where the literature can be found, and you should label this section as “Literature Review.”

➡️ For more information on writing a thesis, visit our guide on how to structure a thesis .

There is no set amount of words for a literature review, so the length depends on the research. If you are working with a large amount of sources, it will be long. If your paper does not depend entirely on references, it will be short.

Take a look at these three theses featuring great literature reviews:

• School-Based Speech-Language Pathologist's Perceptions of Sensory Food Aversions in Children [ PDF , see page 20]
• Who's Writing What We Read: Authorship in Criminological Research [ PDF , see page 4]
• A Phenomenological Study of the Lived Experience of Online Instructors of Theological Reflection at Christian Institutions Accredited by the Association of Theological Schools [ PDF , see page 56]

Literature reviews are most commonly found in theses and dissertations. However, you find them in research papers as well.

There is no set amount of words for a literature review, so the length depends on the research. If you are working with a large amount of sources, then it will be long. If your paper does not depend entirely on references, then it will be short.

No. A literature review should have its own independent section. You should indicate clearly in the table of contents where the literature review can be found, and label this section as “Literature Review.”

The main goal of a literature review is to provide the researcher with sufficient knowledge about the topic in question so that they can eventually make an intervention.

Literature Syntheis 101

How To Synthesise The Existing Research (With Examples)

By: Derek Jansen (MBA) | Expert Reviewer: Eunice Rautenbach (DTech) | August 2023

One of the most common mistakes that students make when writing a literature review is that they err on the side of describing the existing literature rather than providing a critical synthesis of it. In this post, we’ll unpack what exactly synthesis means and show you how to craft a strong literature synthesis using practical examples.

This post is based on our popular online course, Literature Review Bootcamp . In the course, we walk you through the full process of developing a literature review, step by step. If it’s your first time writing a literature review, you definitely want to use this link to get 50% off the course (limited-time offer).

Overview: Literature Synthesis

• What exactly does “synthesis” mean?
• Aspect 1: Agreement
• Aspect 2: Disagreement
• Aspect 3: Key theories
• Aspect 4: Contexts
• Aspect 5: Methodologies
• Bringing it all together

What does “synthesis” actually mean?

As a starting point, let’s quickly define what exactly we mean when we use the term “synthesis” within the context of a literature review.

Simply put, literature synthesis means going beyond just describing what everyone has said and found. Instead, synthesis is about bringing together all the information from various sources to present a cohesive assessment of the current state of knowledge in relation to your study’s research aims and questions .

Put another way, a good synthesis tells the reader exactly where the current research is “at” in terms of the topic you’re interested in – specifically, what’s known , what’s not , and where there’s a need for more research .

So, how do you go about doing this?

Well, there’s no “one right way” when it comes to literature synthesis, but we’ve found that it’s particularly useful to ask yourself five key questions when you’re working on your literature review. Having done so,  you can then address them more articulately within your actual write up. So, let’s take a look at each of these questions.

1. Points Of Agreement

The first question that you need to ask yourself is: “Overall, what things seem to be agreed upon by the vast majority of the literature?”

For example, if your research aim is to identify which factors contribute toward job satisfaction, you’ll need to identify which factors are broadly agreed upon and “settled” within the literature. Naturally, there may at times be some lone contrarian that has a radical viewpoint , but, provided that the vast majority of researchers are in agreement, you can put these random outliers to the side. That is, of course, unless your research aims to explore a contrarian viewpoint and there’s a clear justification for doing so. 

Identifying what’s broadly agreed upon is an essential starting point for synthesising the literature, because you generally don’t want (or need) to reinvent the wheel or run down a road investigating something that is already well established . So, addressing this question first lays a foundation of “settled” knowledge.

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2. Points Of Disagreement

Related to the previous point, but on the other end of the spectrum, is the equally important question: “Where do the disagreements lie?” .

In other words, which things are not well agreed upon by current researchers? It’s important to clarify here that by disagreement, we don’t mean that researchers are (necessarily) fighting over it – just that there are relatively mixed findings within the empirical research , with no firm consensus amongst researchers.

This is a really important question to address as these “disagreements” will often set the stage for the research gap(s). In other words, they provide clues regarding potential opportunities for further research, which your study can then (hopefully) contribute toward filling. If you’re not familiar with the concept of a research gap, be sure to check out our explainer video covering exactly that .

3. Key Theories

The next question you need to ask yourself is: “Which key theories seem to be coming up repeatedly?” .

Within most research spaces, you’ll find that you keep running into a handful of key theories that are referred to over and over again. Apart from identifying these theories, you’ll also need to think about how they’re connected to each other. Specifically, you need to ask yourself:

• Are they all covering the same ground or do they have different focal points  or underlying assumptions ?
• Do some of them feed into each other and if so, is there an opportunity to integrate them into a more cohesive theory?
• Do some of them pull in different directions ? If so, why might this be?
• Do all of the theories define the key concepts and variables in the same way, or is there some disconnect? If so, what’s the impact of this ?

Simply put, you’ll need to pay careful attention to the key theories in your research area, as they will need to feature within your theoretical framework , which will form a critical component within your final literature review. This will set the foundation for your entire study, so it’s essential that you be critical in this area of your literature synthesis.

If this sounds a bit fluffy, don’t worry. We deep dive into the theoretical framework (as well as the conceptual framework) and look at practical examples in Literature Review Bootcamp . If you’d like to learn more, take advantage of our limited-time offer to get 60% off the standard price.

4. Contexts

The next question that you need to address in your literature synthesis is an important one, and that is: “Which contexts have (and have not) been covered by the existing research?” .

For example, sticking with our earlier hypothetical topic (factors that impact job satisfaction), you may find that most of the research has focused on white-collar , management-level staff within a primarily Western context, but little has been done on blue-collar workers in an Eastern context. Given the significant socio-cultural differences between these two groups, this is an important observation, as it could present a contextual research gap .

In practical terms, this means that you’ll need to carefully assess the context of each piece of literature that you’re engaging with, especially the empirical research (i.e., studies that have collected and analysed real-world data). Ideally, you should keep notes regarding the context of each study in some sort of catalogue or sheet, so that you can easily make sense of this before you start the writing phase. If you’d like, our free literature catalogue worksheet is a great tool for this task.

5. Methodological Approaches

Last but certainly not least, you need to ask yourself the question: “What types of research methodologies have (and haven’t) been used?”

For example, you might find that most studies have approached the topic using qualitative methods such as interviews and thematic analysis. Alternatively, you might find that most studies have used quantitative methods such as online surveys and statistical analysis.

But why does this matter?

Well, it can run in one of two potential directions . If you find that the vast majority of studies use a specific methodological approach, this could provide you with a firm foundation on which to base your own study’s methodology . In other words, you can use the methodologies of similar studies to inform (and justify) your own study’s research design .

On the other hand, you might argue that the lack of diverse methodological approaches presents a research gap , and therefore your study could contribute toward filling that gap by taking a different approach. For example, taking a qualitative approach to a research area that is typically approached quantitatively. Of course, if you’re going to go against the methodological grain, you’ll need to provide a strong justification for why your proposed approach makes sense. Nevertheless, it is something worth at least considering.

Regardless of which route you opt for, you need to pay careful attention to the methodologies used in the relevant studies and provide at least some discussion about this in your write-up. Again, it’s useful to keep track of this on some sort of spreadsheet or catalogue as you digest each article, so consider grabbing a copy of our free literature catalogue if you don’t have anything in place.

Bringing It All Together

Alright, so we’ve looked at five important questions that you need to ask (and answer) to help you develop a strong synthesis within your literature review.  To recap, these are:

• Which things are broadly agreed upon within the current research?
• Which things are the subject of disagreement (or at least, present mixed findings)?
• Which theories seem to be central to your research topic and how do they relate or compare to each other?
• Which contexts have (and haven’t) been covered?
• Which methodological approaches are most common?

Importantly, you’re not just asking yourself these questions for the sake of asking them – they’re not just a reflection exercise. You need to weave your answers to them into your actual literature review when you write it up. How exactly you do this will vary from project to project depending on the structure you opt for, but you’ll still need to address them within your literature review, whichever route you go.

The best approach is to spend some time actually writing out your answers to these questions, as opposed to just thinking about them in your head. Putting your thoughts onto paper really helps you flesh out your thinking . As you do this, don’t just write down the answers – instead, think about what they mean in terms of the research gap you’ll present , as well as the methodological approach you’ll take . Your literature synthesis needs to lay the groundwork for these two things, so it’s essential that you link all of it together in your mind, and of course, on paper.

Psst… there’s more!

This post is an extract from our bestselling short course, Literature Review Bootcamp . If you want to work smart, you don't want to miss this .

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Critical Analysis in a Literature Review

3-minute read

• 29th June 2015

A literature review is vital to any in-depth research , providing a foundation your work will build upon. Familiarizing yourself with the existing literature allows you to identify current debates in the field, ensuring that your work is up-to-date and addresses significant questions.

But a good literature review will require reading critically. This means deciding whether you agree or disagree with certain viewpoints, arguments and theories, rather than simply describing them.

It also requires being able to spot the flaws and strengths of particular studies, which can in turn help when developing your own ideas. To make sure you do this effectively, it’s worth looking for the following things.

1. Overgeneralizations

One common issue in research is the scope of its application, especially when dealing with limited sample sizes or when a study is generalized too broadly.

The conclusions of a psychological study conducted with all male participants, for instance, may not be applicable in the same way to female subjects.

2. Methodological Limitations

When writing a literature review, ask yourself whether the methods used for particular studies were appropriate.

For example, whether the study used a quantitative, qualitative or mixed-methods research design can make a big difference to the conclusions reached.

3. How Well Explained is the Research?

When reading for a critical literature review, it is important to consider how well written the studies you examine are.

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Does the author explain their methods? Is enough detail provided for any experiments to be replicated? Are sampling, data collection and analysis techniques clearly identified? Does the conclusion follow from the results?

Asking these and similar questions will help you discern between good and bad research.

4. Identify Biases

Another important factor is to consider whether implicit biases might have influenced the research.

The term “confirmation bias,” for example, refers to the tendency to focus on evidence which supports one’s existing beliefs, which can lead to overlooking alternative hypotheses.

5. Challenge Your Own Assumptions

If you come across a study which seems to oppose your hypothesis, consider whether it presents good counterarguments to your own position. If it does, ask yourself whether this affects how you conduct the rest of your research.

The final point here is important because conducting a literature review serves two purposes . The finished literature review will help your reader to understand the background of your research, so critical analysis helps to clarify what your work contributes to the debate.

But comparing different studies and theories for a literature review will also help you to develop a research approach. The better your critical analysis, then, the better prepared you’ll be.

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• DOI: 10.1177/1534484314536705
• Corpus ID: 145818873

Writing Literature Reviews

• Jamie L. Callahan
• Published 29 June 2014
• Human Resource Development Review

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152 Citations

The art of writing literature review: what do we know and what do we need to know.

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Conducting and Writing a Structured Literature Review in Human Resource Development

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The 5 c's of a literature review.

A Review of Literature

• First Online: 14 March 2021

Cite this chapter

• Samantha S. Reed 4 ,
• Carol A. Mullen 5 &
• Emily T. Boyles 6  

Part of the book series: SpringerBriefs in Education ((BRIEFSEDUCAT))

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This chapter of Problem - Based Learning in Elementary Schools offers a review of the literature addressing problem-based learning (PBL) in elementary classrooms and other educational contexts. Definitions provided generally uphold PBL as a teaching method in which students gain knowledge and skills by working collaboratively to both investigate and respond to authentic and engaging open-ended questions and/or problems. Also described is the history of PBL and its instructional impact on student learning and achievement. In accordance with the current study conducted in Virginia, key strategies of PBL instruction are identified that contribute to 21st-century skills identified nationally and at the state level, which education policy in Virginia denotes as critical thinking, creativity, communication, collaboration, and citizenship (the 5Cs). While exploring the PBL phenomenon and the relevant literature, academic achievement, student impact, and patterns are discussed. At present, much of the existing research focuses on grades K–12 in general terms or postsecondary education. Elementary grades, while investigated, continue to be underrepresented in explorations of PBL, a gap that this book helps to fill.

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Research Article

Clinical outcomes of chikungunya: A systematic literature review and meta-analysis

Roles Data curation, Formal analysis, Methodology, Software, Visualization, Writing – original draft

* E-mail: [email protected]

Affiliation Asc Academics B.V., Groningen, Netherlands

Roles Conceptualization, Writing – original draft

Affiliations Valneva Austria GmbH, Vienna, Austria, Department of Health Sciences, University Medical Center Groningen, Groningen, Netherlands

Roles Conceptualization, Data curation, Methodology, Project administration, Writing – review & editing

Affiliations Asc Academics B.V., Groningen, Netherlands, Department of Health Sciences, University Medical Center Groningen, Groningen, Netherlands

Roles Investigation, Project administration

Roles Data curation, Investigation

Roles Conceptualization, Supervision

Affiliation Valneva Austria GmbH, Vienna, Austria

Roles Supervision

Affiliations Department of Health Sciences, University Medical Center Groningen, Groningen, Netherlands, Department of Economics, Econometrics & Finance, University of Groningen, Faculty of Economics & Business, Groningen, The Netherlands, Center of Excellence for Pharmaceutical Care Innovation, Universitas Padjadjaran, Bandung, Indonesia, Division of Pharmacology and Therapy, Faculty of Medicine Universitas Airlangga, Surabaya, Indonesia

Affiliations Asc Academics B.V., Groningen, Netherlands, Department of Health Sciences, University Medical Center Groningen, Groningen, Netherlands, Department of Health Technology and Services Research, University of Twente, Enschede, The Netherlands

• Kris Rama, 
• Adrianne M. de Roo, 
• Timon Louwsma, 
• Hinko S. Hofstra, 
• Gabriel S. Gurgel do Amaral, 
• Gerard T. Vondeling, 
• Maarten J. Postma, 
• Roel D. Freriks

• Published: June 7, 2024
• https://doi.org/10.1371/journal.pntd.0012254
• Peer Review
• Reader Comments

This is an uncorrected proof.

Chikungunya is a viral disease caused by a mosquito-borne alphavirus. The acute phase of the disease includes symptoms such as fever and arthralgia and lasts 7–10 days. However, debilitating symptoms can persist for months or years. Despite the substantial impact of this disease, a comprehensive assessment of its clinical picture is currently lacking.

We conducted a systematic literature review on the clinical manifestations of chikungunya, their prevalence and duration, and related hospitalization. Embase and MEDLINE were searched with no time restrictions. Subsequently, meta-analyses were conducted to quantify pooled estimates on clinical outcomes, the symptomatic rate, the mortality rate, and the hospitalization rate. The pooling of effects was conducted using the inverse-variance weighting methods and generalized linear mixed effects models, with measures of heterogeneity reported.

The systematic literature review identified 316 articles. Out of the 28 outcomes of interest, we were able to conduct 11 meta-analyses. The most prevalent symptoms during the acute phase included arthralgia in 90% of cases (95% CI: 83–94%), and fever in 88% of cases (95% CI: 85–90%). Upon employing broader inclusion criteria, the overall symptomatic rate was 75% (95% CI: 63–84%), the chronicity rate was 44% (95% CI: 31–57%), and the mortality rate was 0.3% (95% CI: 0.1–0.7%). The heterogeneity between subpopulations was more than 92% for most outcomes. We were not able to estimate all predefined outcomes, highlighting the existing data gap.

Chikungunya is an emerging public health concern. Consequently, a thorough understanding of the clinical burden of this disease is necessary. Our study highlighted the substantial clinical burden of chikungunya in the acute phase and a potentially long-lasting chronic phase. Understanding this enables health authorities and healthcare professionals to effectively recognize and address the associated symptoms and raise awareness in society.

Author summary

Chikungunya disease is an emerging public health concern. The disease is transmitted by mosquitoes and characterized by arthralgia and fever in the acute phase, lasting 7–10 days. Additionally, some individuals experience chronic symptoms such as arthralgia and tiredness that can last from months to years. Chikungunya is mainly present in the Americas and Asian countries, but the mosquitoes transmitting the disease are spreading to other regions due to climate change, amongst others. This increased disease threat highlights the importance of understanding chikungunya symptoms. However, there are currently no precise estimates on the prevalence of chikungunya symptoms. Therefore, we analysed the available literature on the clinical manifestations of chikungunya. We found that 75% of infected people develop symptoms, primarily characterized by arthralgia in 90% and fever in 88% of cases. Chronic symptoms affect 44% of symptomatic people, and 0.3% of patients with chikungunya die. Unfortunately, we were not able to estimate all predefined outcomes of interest because we did not find enough studies publishing on some of these, demonstrating that there is still much unknown around the clinical manifestations of chikungunya. However, the results can help healthcare workers early identifying chikungunya and raise awareness of this debilitating disease.

Citation: Rama K, de Roo AM, Louwsma T, Hofstra HS, S. Gurgel do Amaral G, Vondeling GT, et al. (2024) Clinical outcomes of chikungunya: A systematic literature review and meta-analysis. PLoS Negl Trop Dis 18(6): e0012254. https://doi.org/10.1371/journal.pntd.0012254

Editor: Richard A. Bowen, Colorado State University, UNITED STATES

Received: February 26, 2024; Accepted: May 28, 2024; Published: June 7, 2024

Copyright: © 2024 Rama et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the manuscript and its Supporting information files.

Funding: This paper was funded by Valneva Austria GmbH. AMR and GTV are Valneva employees. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: KR, TL, HSH, and GSG are employees of Asc Academics. Asc Academics has received consultancy fees for this project from Valneva Austria GmbH. AMR and GTV are Valneva employees and own stock options of Valneva. MJP reports grants and honoraria from various pharmaceutical companies, including those developing, producing, and marketing vaccines. He holds stocks in Health-Ecore (Zeist, Netherlands) and PAG BV (Groningen, Netherlands), and advises ASC Academics (Groningen, Netherlands). These competing interest will not alter adherence to PLOS policies on sharing data and materials.

Introduction

Chikungunya is a viral disease caused by a mosquito-borne alphavirus, the chikungunya virus (CHIKV) [ 1 ]. The infection is characterized by an acute phase with symptoms including fever, arthralgia, and myalgia. While most infected individuals fully recover after the acute phase of the disease, between 30–40% of patients develop persistent symptoms, such as chronic arthritis, fatigue, stiffness, depression, and sleep and neurological disorders, which can last from months to several years [ 2 , 3 ]. Long-term effects lead to significant limitations in daily activities and reduce the patients’ overall quality of life [ 4 – 6 ]. Nevertheless, despite the negative impact of the disease on the quality of life, the awareness and societal understanding of chikungunya remain limited, even among the afflicted populations and healthcare workers [ 7 ]. Chikungunya has been identified as a public health threat based on several records of CHIKV outbreaks worldwide, with a risk of exacerbation in the future due to the global spread of CHIKV [ 8 ]. The distribution of the CHIKV vectors ( Aedes aegypti and Aedes albopictus ) is one of the main factors contributing to the disease’s dissemination. This expansion is attributed to globalization and climate change, allowing the Aedes mosquitos to survive in areas previously considered unsuitable [ 9 , 10 ]. Prevention against the disease consists predominantly of mosquito population control [ 11 ]. Recently, the FDA approved the first chikungunya vaccine, presenting a new tool to fight the disease and potentially alleviate the associated economic and health burdens [ 12 ]. Despite the increasing interest in CHIKV and the recent announcement of a vaccine, uncertainties persist regarding the clinical burden of chikungunya. Although multiple studies have explored one or more health outcomes associated with chikungunya [ 3 , 13 , 14 ], to the best of our knowledge, no extensive meta-analysis was performed to quantify pooled estimates on the clinical presentation of chikungunya. To address this gap, we conducted a comprehensive systematic literature review (SLR) on the clinical manifestations of chikungunya, and proceeded with a robust yet flexible meta-analysis. This approach allowed us to provide estimates on a broad spectrum of endpoints on the health outcomes of chikungunya. We paid particular attention to the symptomatic, mortality, and chronicity rates for a comprehensive understanding of the disease in both acute and chronic phases. Our study aims to contribute valuable insights into the overall clinical outcomes of chikungunya. This, in turn, can inform public health intervention strategies and enhance global surveillance by enabling earlier detection of outbreaks.

Literature search and study selection

The SLR adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 (PRISMA 2020) guidelines, with searches conducted on MEDLINE In-Process via PubMed.com, and Embase via Embase.com without time limits. Grey literature searches were performed for the years 2019–2023 to capture data that may not have yet been included in the databases. The search string included terms related to chikungunya and study design. Eligibility criteria were developed using a Population, Intervention, Comparator, Outcomes, Study (PICOS) framework. The inclusion criteria focused on the clinical manifestations of chikungunya, their prevalence and duration, and related hospitalization, and excluded in vitro/preclinical studies, reviews, and non-English articles. Specifics can be found in S1 Text .

Screening and data extraction

All retrieved articles were deduplicated and titles and abstracts were screened against the PICOS criteria using Rayyan. From the selected articles, full texts were examined for eligibility, followed by detailed data extraction organized by study design, patient characteristics, and outcomes of interest. The whole screening process was conducted by two independent reviewers (GG, HH), resolving conflicts through consensus. An exhaustive feasibility assessment ensured the inclusion of studies with explicit criteria and comparable reporting methods, reducing heterogeneity and potential outlier influence. The risk of bias was determined using a modified Downs and Black checklist [ 15 ] and NIH quality assessment tool for observational studies [ 16 ], see S2 Text . Discrepancies were resolved by consensus. No protocol for this systematic review and meta-analysis was registered.

Population and data analysis

The meta-analysis was performed using the meta package of the R statistical software to create a pooled estimate of the most important clinical outcomes of chikungunya. The outcomes of interest were the overall symptomatic, chronicity, and mortality rates, the underreporting factor, the duration of the acute and chronic phase, the hospitalization and outpatient rate (acute and chronic), the mortality rate per region, and the rate and duration of the following symptoms: arthralgia, arthritis, fatigue, fever, headache, joint swelling, myalgia, nausea, rash, and vomiting. The distinction between arthralgia and arthritis was made based on the definition used in the original study.

Both fixed-effects and random-effects models with logit transformation were estimated, where a random-effects model was chosen in case of high heterogeneity. Fixed-effects meta-analyses employed inverse-variance weighting, while random-effects accounted for between-study heterogeneity and are better suited to account for the larger variations in outcomes reported. Heterogeneity was assessed using Cochran’s Q , I 2 , H 2 statistics, and τ 2 estimation. Outlier analyses employed the leave-one-out method, Baujat plots, and statistical distance measures. All results were visually represented using forest plots, providing a clear and concise graphical representation of the individual study findings and the overall meta-analysis result.

Our study utilized subpopulations—subsets of the original populations defined by particular demographic and clinical features. These features correspond to the data reported in the studies we analyzed and the segmentation into subpopulations was based on the inclusion or exclusion criteria set forth in the original research papers. This approach allowed us to perform a more granular analysis. The clinical outcomes of interest were analyzed for a target population to ensure comparability among included studies, which excluded children under 15, individuals with comorbidities or concurrent infections, and pregnant women. Additionally, we excluded unconfirmed CHIKV cases and studies involving chronic patients reporting on the acute phase due to recall bias. Lastly, retrospective studies focusing on mortality were excluded as they exhibited evidence of selection bias. Meta-analyses were performed when an endpoint was reported at least five times for a given subpopulation.

A preliminary search indicated that data on chronicity, mortality, and symptomatic cases was predominantly reported for a more general population, including individuals under the age of 15 and chronic patients. Therefore, we decided to apply less strict criteria on the studies reporting these outcomes, allowing us to estimate these endpoints. Additionally, to detail the development of chronic symptoms, we estimated the chronic rate at various points from disease onset by dividing studies reporting on chronicity rates following a CHIKV infection into subgroups based on time intervals (three, six, and 12 months). The inclusion criteria for each subgroup were to fall within the time windows created by consecutive intervals (e.g., 90–180 days for three months). We excluded studies extending beyond 24 months to avoid a selection bias, as these already focused on patients with pre-existing chronic conditions.

For the mortality rates, we separated the groups that reported outcomes for high-risk populations from those dealing with the general population with lower risk. This stratification allowed us to account for potential confounding variables. Older age and comorbidities have been identified to increase the risk for mortality [ 2 , 17 ]. Therefore, we classify as high-risk of mortality the groups with a minimum age over 65 (or median above 70 when missing), and previous conditions that induced prior intensive care exceeding 24 hours.

To estimate the overall symptomatic rate, we included studies that explicitly reported symptomatic rates based on one or more of the symptoms commonly associated with the disease. Symptomatic patients were often an implicit inclusion criteria, or a precondition for laboratory testing, making most of the studies reporting on the symptomatic rate unusable. We excluded the studies that had a 100% symptomatic rate to prevent selection bias, as including those would lead to a skewed perspective due to symptoms being part of their inclusion criteria.

Literature search

The SLR was conducted on 4 July 2023 and yielded 16,308 hits. After removing 6,285 duplicates, 10,023 studies were screened by titles and abstracts. From these, a total of 316 articles were deemed suitable for inclusion. The process of the SLR is detailed in Fig 1 , which illustrates the PRISMA diagram of the included studies. The complete PRISMA checklist is provided in S3 Text . The quality assessment of included studies can be found in S1 Table .

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• TIFF original image

https://doi.org/10.1371/journal.pntd.0012254.g001

Study characteristics

The categorization of study designs in the included articles was made with careful consideration, taking into account the diversity in how these studies defined their methodologies. The judgment used in categorizing these studies was guided by the definitions provided within the paper itself. When a study described its design in a way that matched more than one predefined category, the predominant one was chosen. This approach aimed to respect the original terminology used by the study authors while also creating a coherent framework for analysis.

Of the 316 articles included, 231 studies were observational, 11 were experimental, and for 74 studies this was not reported. Of the observational studies, 106 were cross-sectional, 35 were cohort, 29 were longitudinal, 25 were retrospective, 23 were prospective, and 13 were case-control or case-series studies. Of the experimental studies, there were 6 trials from phase I to III with double and single-blind designs. Goals ranged from assessing treatments like chloroquine and vaccines’ effectiveness to exploring seroprevalence and chronic CHIKV effects. Two trials investigated new mRNA treatment mechanisms. The focus was solely on CHIKV, not on coinfections.

The study location varied: Southern Asia was the most represented with 78 articles, followed by South America, with 67. There were 41 articles from The Caribbean region, 41 from Eastern Africa, 28 from South-Eastern Asia, 14 from Central America. Eight, six, five, four, and three articles were from Western Europe, Northern America, Southern Europe, Middle Africa, and Western Africa, respectively. Two or one articles were from Eastern Asia, Micronesia, Northern Europe, or Southern Africa. A total of 193 studies reported mean or median age. Data on co-infection with Zika and/or dengue were reported in 11 studies. An overview of the study characteristics, including details on the experimental studies, can be found in S2 Table .

The most commonly reported symptom was fever, reported in 57.9% of the studies (N = 183), followed by rash in 54.1% (N = 171), headache in 51.3% (N = 162), and arthralgia in 47.8% (N = 151). Most studies reported high rates (70% to 100%) of fever. Among the 151 studies reporting arthralgia rates, the symptom prevalence ranged from 1% to 100%, as studies presented heterogeneous settings, including, for example, recovered patients, patients in the acute phase, or chronic patients. Duration of symptoms was reported in 22 studies. Taking all symptoms into account, the mean duration of symptoms ranged from two days (fever) to 342 days (arthralgia). It is important to note that the studies presented heterogeneous groups of patients when reporting on the duration of symptoms, which could explain the wide range reported in literature. The hospitalization rate was reported by 53 studies. The hospitalization rate varied between 0%, reported by five different studies [ 18 – 22 ], and 93% in a study by Reller and colleagues [ 23 ].

The development of chronic disease after CHIKV infection was reported in 68 studies. Most studies defined chronic CHIKV infection as the presence of symptoms three months after the infection. Arthralgia was reported as a chronic symptom in 67 studies, joint swelling was reported in 11 studies, myalgia was reported in eight studies, stiffness, especially in the morning, was reported in six studies, and arthritis was reported in four studies. The percentage of patients developing chronic disease ranged from 16% in a study conducted during an outbreak in Chennai, India [ 24 ] to 100% in two other studies [ 25 , 26 ]. Fifty of the included studies reported data on mortality, of which 22 reported no deaths in the study population. The highest reported mortality rate was 36.67%, or 36,670 per 100,000 population, reported by Gupta and colleagues. This study population consisted of chikungunya patients who had been admitted to the intensive care [ 27 ].

Meta-analyses feasibility and results

From the 316 articles retrieved from the SLR, we extracted 756 distinct subpopulations. Each subpopulation corresponds to a group defined by a unique set of inclusion and exclusion criteria as per the definitions provided in each original study. Out of the 756 subpopulations, 335 were used for the analysis of the general population, while 52 where used for the target population. From the 28 selected clinical outcomes, we were able to conduct 11 meta-analyses for the target population, see Fig 2 . The number of studies and subpopulations available for each endpoint is shown in Table 1 . The forest plots from the individual meta-analyses can be found in S1 Fig , and the outlier analysis for each endpoint with the Baujat plot is presented in S2 Fig . No studies or subpopulations were excluded based on outlier analyses. Below, we present the 11 estimates from the meta-analyses on the target population, followed by the results of the analysis on mortality, chronicity, and overall symptomatic rates in the general population.

https://doi.org/10.1371/journal.pntd.0012254.g002

Presented are the number of studies and number of subpopulations reporting on the specific outcomes, the pooled estimates, confidence intervals and I 2 of the estimated endpoints. CI: confidence interval. I 2 : I-squared statistic of heterogeneity.

https://doi.org/10.1371/journal.pntd.0012254.t001

Chikungunya symptoms estimates in the target population.

The prevalence of arthralgia in symptomatic adults with confirmed chikungunya was estimated at 89.7%, while arthritis was less frequent at 17.6%. Fatigue was observed in 56% of patients, fever in 87.8%, and headache affected 49.5% of the population. Joint swelling was reported in 50% of patients, myalgia in 62.9%, nausea in 34.7%, rash in 44.3%, and vomiting in 17.1%. The hospitalization rate during the acute phase of chikungunya was reported by nine subpopulations and estimated at 17%. All results are presented in Table 1 , showing the pooled effect estimate for each symptom, reflecting the average rate of occurrence in the studied populations within specified confidence intervals. Each symptom analysis showed substantial heterogeneity between subpopulations, indicated by high I 2 statistics.

Chronicity, mortality, and overall symptomatic rate.

The meta-analysis for chronicity rate showed declining rates over time: 43.89% at three months, 34.39% at six months, and 31.87% at twelve months, see Fig 3 . Notably, persistent high heterogeneity was observed across subgroups ( I 2 between 96–97%). Mortality rates were estimated at 0.32% (320 per 100,000 population), for normal-risk populations and 15.34% (15,340 per 100,000 population) for high-risk populations, see Fig 4 . The latter displayed higher heterogeneity ( I 2 = 97%) compared to the normal risk ( I 2 = 87%). The meta-analysis estimates that 74.9% of the general population with CHIKV infection were symptomatic, with a 95% confidence interval from 63% to 84%, see Fig 5 . A total of eight studies with corresponding eight subgroups were included in this analysis. I 2 statistics showed a heterogeneity of 91%. Results of the outlier and influential cases analysis can be found in S2 Fig .

https://doi.org/10.1371/journal.pntd.0012254.g003

https://doi.org/10.1371/journal.pntd.0012254.g004

https://doi.org/10.1371/journal.pntd.0012254.g005

Chikungunya poses an emerging global health threat; however, uncertainties around the health burden of this infectious disease persist. This SLR and meta-analyses aim to consolidate existing research on the clinical manifestations of chikungunya. The objective of this study was to provide accurate estimates on the symptomatology of this disease, with a specific focus on the chronicity, mortality, and overall symptomatic rates. Overall, our findings emphasize the substantial disease burden associated with a CHIKV infection.

Arthralgia, fever, and myalgia were the most prevalent symptoms, affecting 89.7%, 87.8%, and 62.9% of symptomatic adults, respectively. These symptoms are also described in previous literature as most common for chikungunya [ 17 , 28 ]. It’s important to note that these symptoms were often implicitly used when initially detecting suspected cases. Although we removed all explicit inclusion criteria, these estimates are likely affected by selection bias. The hospitalization rate of 17% underscores the challenges for healthcare systems during outbreaks. The disease burden related to these symptoms makes chikungunya a significant burden for local healthcare systems, highly influencing the quality of life of infected individuals [ 6 ].

The number of studies that provided data on mortality, chronicity, and overall symptomatic rate was limited for the target adult population. Thus, we decided to use less restrictive population criteria for these specific outcomes. Within this broader general population, we found a 0.32% (320 per 100,000 population) mortality rate in the low-risk group. This is slightly higher than the common reported case-fatality rate of 0.1% (100 per 100,000 population), although reports on mortality rated may vary [ 2 , 6 ]. To our knowledge, no previous meta-analysis on mortality rates has been performed. Therefore, we argue that 0.32% (320 per 100,000 population) is a realistic estimate for the general population. While this percentage is still relatively low compared to other arboviruses [ 29 ], mortality rates can be drastically higher in high-risk groups. Our meta-analysis revealed a mortality rate of 15.34% (15,340 per 100,000 population) in elderly and individuals with previous emergency department or intensive care admissions.

In defining the high-risk group for mortality, we included hospitalized patients who are typically older. As a result, the average age within this group was higher and advanced age is a recognized risk factor for increased mortality from CHIKV infection [ 30 ]. The task of separating the effects of comorbid conditions from the direct impact of CHIKV on mortality rates is complex. These factors often interact with each other, complicating the attribution of cause of death to CHIKV alone—particularly when our analysis could not conclusively establish the causes listed on death certificates. Furthermore, we recognize the possibility of publication bias in existing research on severe CHIKV cases. There may be an overrepresentation of studies focusing on severe outcomes and elevated mortality rates among individuals with underlying health complications or atypical presentations of CHIKV. Such a bias could lead to an overestimation of the mortality risk associated with the virus. Nonetheless, our SLR showed mortality rates up to 36.67% (36,670 per 100,000 population) in specific populations, demonstrating that despite its low rates in the general population, the impact of mortality should not be overlooked [ 27 ].

The chronic phase of chikungunya can be debilitating and long-lasting, leading to a significant health burden for individuals affected. Results from our meta-analysis showed a chronicity rate of 43.89% at three months, 34.39% at six months, and 31.87% at 12 months post-infection, indicating the lasting health burden. A meta-analysis conducted by Paixao and colleagues on the chronicity rate of chikungunya showed similar outcomes, with an overall no-recovery rate of 43% after three months [ 3 ]. One notable difference, possibly due to variations in methodologies, is that Paixao and colleagues reported slightly lower rates over time. Both studies indicate a stabilization over time, but more research is needed to comprehensively map the progression of the chronic phase. In conclusion, long-term chronic illness majorly impacts the quality of life of chikungunya patients [ 4 , 6 ], making these results alarming, especially in light of the potential growing spread of the disease [ 9 , 10 ].

The significant disease burden related to chikungunya was further underlined by an overall symptomatic rate of 74.9% in the general population. The symptomatic rate of chikungunya was estimated between 72% and 97% by the CDC Yellow Book, showing that our estimate could be on the low end [ 17 ]. A reason for this could be the various definitions of symptomatic manifestations across studies, which posed a challenge in deriving a precise estimate for this outcome. Additionally, estimates in the literature are mainly based on patients showing healthcare-seeking behaviour, leaving out asymptomatic patients. Therefore, these estimates are likely to be overestimated. Because we created our estimate based on the total general population, we expect them to provide a better reflection of reality.

Two studies identified in the SLR were designed to investigate treatment options for Chikungunya and therefore included control groups. However, we excluded control populations without confirmed CHIKV from our analysis because our focus was on populations with confirmed CHIKV. In instances where multiple treatment options were assessed among confirmed CHIKV populations, these groups were included in the analysis as we aimed to understand the symptomatology of the disease at presentation in its acute phase. It should be noted that the inclusion of these populations did not significantly influence the outcomes of our study since the primary interest was in the manifestation of symptoms rather than treatment efficacy.

Although we obtained estimates for 11 of the 28 predefined endpoints, estimation for several endpoints proved infeasible due to their infrequent reporting as identified in the SLR. We did not obtain estimates for the underreporting factor, the length of the acute and the chronic phase, the duration of the different symptoms, and the frequencies of hospitalization and outpatient care. Even considering the subpopulation analysis method used, we could not estimate more endpoints. The limited number of studies reflects the uncertainty and novelty associated with chikungunya and the need for more research in this field.

In cases where meta-analyses were feasible for the endpoints, we encountered challenges due to poor data quality or absent data. This is attributable to two main reasons: firstly, the reporting of several endpoints varied inconsistently across studies, preventing their combination in a meta-analysis; and secondly, some studies that reported the desired endpoint did not meet the inclusion criteria, resulting in sparse data that hindered meaningful analysis. As a result, significant knowledge gaps persist regarding various aspects of chikungunya. Further research is necessary to fill these gaps and enhance our understanding of this disease. Additionally, consistent and strict reporting criteria on the clinical picture of chikungunya are needed to help create more comprehensive estimates. Enhanced quality and quantity of data could facilitate the possibility to study potential differences in symptomatology for the different CHIKV subtypes. Furthermore, it could enable investigations into the pathogenicity of CHIKV over the years by comparing data from previous outbreaks.

A strength of our study is the use of subpopulation analyses. We discovered that extracting subpopulations from individual studies allows more endpoints to be estimated, offering comparable populations that limit heterogeneity. The use of subgroups could be useful for future research and mitigate some of the data discrepancies detected in the SLR.

The main limitation of our study is the significant presence of heterogeneity indicated by an average I 2 statistic of 92%. This reflects substantial differences in the inclusion criteria among the studies, a tendency inherent in the disease area of CHIKV as shown by other meta-analyses reporting similar, or even higher, levels of heterogeneity [ 3 ]. There are several reasons for this high heterogeneity. First, data collection on chikungunya is conducted mostly during the outbreaks which limits the possibility of establishing strict scientific protocols as researchers must adapt to the dynamic nature of the event. Secondly, a standardized methodology for reporting endpoints is lacking, making it challenging to compare studies in a meta-analysis. Thirdly, we noticed that including older individuals affected our results, by showing lower symptomatic rates but higher mortality and hospitalization rates. Future studies might exclude this demographic for more precise age-related outcomes. Additionally, other, less known, symptoms might have influenced the disease estimates. An example of this is depressive symptoms related to chikungunya. A study included in our analysis has potentially skewed our meta-analysis results with inflated estimates for fatigue, headache, and rash because they investigated depressive symptoms during the CHIKV infection [ 31 ]. This highlights how undisclosed factors that increase the population’s vulnerability to chikungunya symptoms can potentially impact the research. Another limitation is the potential for confounding factors contributing to symptom prevalence, which we were unable control for in our study. There’s an implicit assumption that the symptoms described have a causal association with Chikungunya; however, some symptoms such as myalgia and fatigue are commonly prevalent in the population and may not be causally related to CHIKV infection. The difficulty in establishing a direct causal relationship between these symptoms and CHIKV should be taken into consideration when interpreting the results. We acknowledge that this could affect the precision of the associations drawn in our analysis and suggest that future research should aim to discern the specific attributable risk of CHIKV for these symptoms. Lastly, outbreaks often occur in locations with limited surveillance systems, leading to lacking or less accurate data from these areas. The high heterogeneity shows the need for additional research in the fields, as well as standardized methodologies in studying chikungunya. Additionally, it emphasizes the importance of meta-analyses like these to come to accurate estimates.

Chikungunya is recognized as a global public health threat, and the disease is expected to spread further due to globalization and climate change. At the same time, vector control and surveillance systems remain limited. Consequently, a thorough understanding of the clinical burden of chikungunya is important to inform public health intervention strategies and improve global surveillance. Our study showed that chikungunya poses a significant health burden, with 74.9% of infected individuals experiencing symptomatic disease. Chronic symptoms are found in 43.4% of patients and can be debilitating and long-lasting. We were not able to create pooled estimates on all endpoints, highlighting the still existing data gap in literature here. Nevertheless, the outcomes determined add to the growing body of evidence underlining the debilitating consequences of chikungunya. With the growing threat of chikungunya, health authorities and healthcare professionals must be prepared to adequately diagnose patients affected by the disease and consider public health interventions to limit its burden. Our findings contribute to the comprehension of chikungunya’s clinical outcomes, essential for improving global surveillance and detecting potential outbreaks.

Supporting information

S1 text. literature search and study selection..

Containing the search strategy and PICOs of the studies included in the SLR.

https://doi.org/10.1371/journal.pntd.0012254.s001

S2 Text. Quality assessment tools.

Modified Downs & Black checklist and the NIH quality assessment tool.

https://doi.org/10.1371/journal.pntd.0012254.s002

S3 Text. PRISMA 2020 checklist.

https://doi.org/10.1371/journal.pntd.0012254.s003

S1 Table. Quality assessment of included studies.

https://doi.org/10.1371/journal.pntd.0012254.s004

S2 Table. Summary of study characteristics.

https://doi.org/10.1371/journal.pntd.0012254.s005

S1 Fig. Forest plots of the clinical outcomes of chikungunya.

https://doi.org/10.1371/journal.pntd.0012254.s006

S2 Fig. Influential case and outlier analysis with Baujat plots.

https://doi.org/10.1371/journal.pntd.0012254.s007

Acknowledgments

We would like to thank the internal teams of Asc Academics who helped during the data extraction phase of the SLR, as well as Roma Kwiatkiewicz from Asc Academics for providing medical writing support.

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• Open access
• Published: 01 December 2022

The psychological impact, risk factors and coping strategies to COVID-19 pandemic on healthcare workers in the sub-Saharan Africa: a narrative review of existing literature

• Freddy Wathum Drinkwater Oyat 1 ,
• Johnson Nyeko Oloya 1 , 2 ,
• Pamela Atim 1 , 3 ,
• Eric Nzirakaindi Ikoona 4 ,
• Judith Aloyo 1 , 5 &
• David Lagoro Kitara   ORCID: orcid.org/0000-0001-7282-5026 1 , 6 , 7  

BMC Psychology volume  10 , Article number:  284 ( 2022 ) Cite this article

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The ongoing COVID-19 pandemic has significantly impacted the physical and mental health of the general population worldwide, with healthcare workers at particular risk. The pandemic's effect on healthcare workers' mental well-being has been characterized by depression, anxiety, work-related stress, sleep disturbances, and post-traumatic stress disorder. Hence, protecting the mental well-being of healthcare workers (HCWs) is a considerable priority. This review aimed to determine risk factors for adverse mental health outcomes and protective or coping measures to mitigate the harmful effects of the COVID-19 crisis among HCWs in sub-Saharan Africa.

We performed a literature search using PubMed, Google Scholar, Cochrane Library, and Embase for relevant materials. We obtained all articles published between March 2020 and April 2022 relevant to the subject of review and met pre-defined eligibility criteria. We selected 23 articles for initial screening and included 12 in the final review.

A total of 5,323 participants in twelve studies, predominantly from Ethiopia (eight studies), one from Uganda, Cameroon, Mali, and Togo, fulfilled the eligibility criteria. Investigators found 16.3–71.9% of HCWs with depressive symptoms, 21.9–73.5% with anxiety symptoms, 15.5–63.7% experienced work-related stress symptoms, 12.4–77% experienced sleep disturbances, and 51.6–56.8% reported PTSD symptoms. Healthcare workers, working in emergency, intensive care units, pharmacies, and laboratories were at higher risk of adverse mental health impacts. HCWs had deep fear, anxious and stressed with the high transmission rate of the virus, high death rates, and lived in fear of infecting themselves and families. Other sources of fear and work-related stress were the lack of PPEs, availability of treatment and vaccines to protect themselves against the virus. HCWs faced stigma, abuse, financial problems, and lack of support from employers and communities.

The prevalence of depression, anxiety, insomnia, and PTSD in HCWs in sub-Saharan Africa during the COVID-19 pandemic has been high. Several organizational, community, and work-related challenges and interventions were identified, including improvement of workplace infrastructures, adoption of correct and shared infection control measures, provision of PPEs, social support, and implementation of resilience training programs. Setting up permanent multidisciplinary mental health teams at regional and national levels to deal with mental health and providing psychological support to HCWs, supported with long-term surveillance, are recommended.

Peer Review reports

Introduction

When coronavirus disease 2019 (COVID-19) was declared a pandemic in March 2020, healthcare workers (HCWs) globally and in sub-Saharan Africa (SSA) were unprepared for the scale of the physical and mental health devastation that was to follow [ 1 ]. The impact of the COVID-19 pandemic on healthcare workers has been profound, characterized by death, disability, and untenable burden on mental health and well-being [ 2 ]. Factors impacting their mental health include high risks of exposure and infection, financial insecurity, separation from loved ones, stigma, difficult triage decisions, stressful work environment, scarcity of supplies including personal protective equipment (PPEs), exhaustion, traumatic experiences due to regular witnessing of deaths among patients and colleagues [ 2 , 3 ]. Greenberg et al. [ 4 ] observed that the COVID-19 pandemic put healthcare professionals worldwide in an unprecedented situation, making difficult decisions to provide care for many severely ill patients with constrained or inadequate resources.

In almost all WHO regions, data indicates that infection rates among healthcare workers are higher than in the general population [ 5 ]. Scholars suggest that the end of the COVID-19 pandemic is not yet in sight. Neither are they sure about the virulence of the following variant when it appears as caseloads are still rising, with more than 621 million infections and 6.5 million deaths reported worldwide by 19th October 2022 [ 6 ]; mainly driven by the newer omicron variants. However, recently in October 2022, we received with gratitude a reassuring message from US President Biden declaring the end of the COVID-19 pandemic in the United States of America.

Meanwhile, previous studies found high levels of depression, anxiety, and PTSD in survivors among the general population and healthcare workers (HCWs) one-to-three years after the control of the SARS epidemic [ 7 ] and the 2014–2016 Ebola epidemic in West Africa [ 8 ]. In addition, recent surveys [ 9 , 10 , 11 , 12 , 13 , 14 ], reviews, and meta-analyses [ 15 , 16 , 17 , 18 ] are pointing to early evidence that a considerable proportion of healthcare workers have experienced stress, anxiety, depression, and sleep disturbances during the COVID-19 pandemic, raising concerns about risks to their long-term mental health.

Studies from the global north countries [ 19 , 20 ], UK [ 21 ], USA [ 22 ], and in India [ 23 ], and China [ 24 , 25 ] have shed light on the vulnerability that characterizes frontline healthcare workers during this pandemic, especially regarding their mental health and well-being. However, evidence in sub-Saharan Africa is scanty, and the pattern and prevalence of psychological disorders are not well understood.

Evidence from a systematic review by Pappa S et al. on 33,062 Chinese HCWs in April 2020 found a pooled prevalence rate of mental health problems among respondents; anxiety 23.2%, depression 22.8%, and insomnia 38.9% [ 26 ]. Similarly, Singapore study, Tan et al . [ 27 ], Li et al . [ 28 ], BMA [ 29 ] and in China [ 31 ] found high levels of psychological disorders among health workers.

Since the beginning of the pandemic, we found one systematic review involving 919 frontline HCWs, 3928 general HCWs, and 2979 medical students conducted in Africa from December 2019 to April 2020 [ 31 ]. The study by Chen J et al . reported a high prevalence of depression, anxiety, and insomnia among frontline HCWs in sub-Saharan Africa (SSA) at 45%, 51%, and 28%, respectively. In comparison, the prevalence of depression, anxiety, and insomnia among the general population was much lower at 30%, 31%, and 24%, respectively [ 31 ]. Furthermore, we found that only a few studies investigated protective and coping measures, given the many uncertainties surrounding the evolution of the COVID-19 pandemic [ 32 ]. Adequate data are needed to equip frontline HCWs and healthcare managers in sub-Saharan Africa to mitigate the medium and long-term adverse effects of the COVID-19 pandemic [ 33 ].

This review aimed to answer three questions (1) What is the psychological impact of the COVID-19 pandemic on HCWs in Sub-Saharan Africa?

(2) What are the associated risk factors during the COVID-19 pandemic?

(3) What interventions (mitigating and coping strategies) protect and support the mental health and well-being of HCWs during the ongoing crises and after the pandemic?

Methodology

Search methodology and article selection.

This current article is a mixed-method narrative review of existing literature on mental health disorders, risk factors, and interventions relevant to the COVID-19 pandemic on HCWs in sub-Saharan. A search on the PubMed electronic database was undertaken using the search terms "novel coronavirus", "COVID-19", "nCoV", "mental health", "psychiatry", "psychology", "anxiety", "depression" and "stress" in various permutations and combinations.

Search processes

We conducted a comprehensive literature search on original articles published from March 2020 to 30 April 2022 in electronic databases of Embase, PubMed, Google Scholar, and the daily updated WHO COVID-19 database. Our search terms included but were not limited to ('COVID-19'/exp OR COVID-19 OR 'coronavirus'/exp OR coronavirus) AND ('psychological'/exp OR psychological OR 'mental'/exp OR mental OR 'stress'/exp OR stress OR 'anxiety' OR anxiety OR 'depression' OR depression OR 'post-traumatic' OR 'post-traumatic'/exp OR 'trauma' OR 'trauma'/exp) OR Health care workers, medical workers of health care professionals, sub-Saharan Africa, for Embase. ("COVID-19" [All Fields] OR "coronavirus" [All Fields]) AND ("Stress, Psychological" [Mesh] OR "mental" OR "anxiety" OR "depression" OR "stress" OR "post-traumatic" OR "trauma") for PubMed, for the WHO COVID-19 database, and ("COVID-19" OR "coronavirus") AND ("Psychological" OR "mental" OR "anxiety" OR "depression" OR "stress" OR "post-traumatic" OR "trauma") for Google Scholar. On reviewing the above citations, twelve articles met the inclusion criteria relevant for this review and are in Table 1 . All twelve articles were cross-sectional, with one qualitative and the others quantitative observational studies.

Eligibility criteria

We included original qualitative and quantitative studies examining the risk factors, psychological impact of COVID-19 and coping strategies of healthcare workers (HCWs) in sub-Saharan Africa during the COVID-19 pandemic. We excluded studies if they were.

1. Not reported in the English language 2. Studies which were not primary research 3. Studies that had not been published in a peer-reviewed journal 4. Studies that did not include data on HCWs’ mental health or psychological well-being 5. Duplicate studies 6. not using validated instruments to measure the risks and psychological impact.

FWDO performed the search of articles. DLK reviewed the articles involving screening of titles, followed by examination of abstracts. The potential articles identified were further reviewed in full text to examine their eligibility. In addition, four of the authors independently reviewed the full articles to abstract the relevant data required for the review. Thereafter, a meeting to harmonise findings were done and presented in a report.

Data extraction and appraisal of the study

We extracted information from each study, including author, study population, year of publication, country, socio-demographic characteristics, sample size, response rate, gender proportion, age, and study time, areas assessed, the validated instrument used and the prevalence. The appraisal involved assessing the research design, recruitment of respondents, inclusion and exclusion criteria, reliability of outcome determination, statistical analyses, ethical compliance, strengths, limitations, and clinical implications of the articles.

Our review protocol was not registered on PROSPERO because of the significant variation in the methodologies of the articles used in the review. The results precluded using a meta-analytic approach and made a narrative review the most suitable for this work. In addition, we did not use the Cochrane Collaboration GRADE method to assess the quality of evidence of outcomes included in this narrative review. Instead, we used the Strengthening the Reporting of Observational studies in Epidemiology (STROBE) 22 items checklist to gauge the quality of the twelve articles included in this review. We qualitatively validated the articles based on additional considerations namely study design, sample sizes, sampling procedures, response rates, statistical methods used, measures taken by the authors to deal with bias and confounding factors and ethical consideration.

Definition of healthcare worker (HCW)

For this narrative review, we adhered to the Centres for Disease Control and Prevention (CDC) definition of HCWs, which includes physicians, nurses, emergency medical personnel, dental professionals and students, medical and nursing students, laboratory technicians, pharmacists, hospital volunteers, and administrative staff [ 34 ].

Search results

The search found twenty-three studies of interest. Full texts of potentially relevant studies underwent eligibility assessment, and twelve articles met the inclusion criteria for this narrative review.

Study characteristics

The twelve articles comprised eleven quantitative and one qualitative study. The common mental health conditions assessed were depression, anxiety, perceived stress, and post-traumatic stress disorder (PTSD). The coping strategy, perceived health status, health distress (including burnout), insomnia, and perceived stigma were also assessed [ 35 , 36 ]. The total number of respondents in these studies was 5,323. The qualitative study had fifty respondents [ 35 ], while the most significant number of participants, 420 was recorded in one of the quantitative studies from Ethiopia [ 37 ]. The questionnaire response rates varied between 90%-100%, with most studies dominated by male respondents at 51.9%-69.2% [ 38 ]. Nurses were the commonest study population, followed by doctors, pharmacists, and laboratory technicians, and no study involved non-HCWs of facilities. Most papers utilized probability sampling procedures, and four quantitative studies used non-random sampling procedures limiting generalizability of their findings and increasing the risk of selection bias. Eight studies were from Ethiopia, and one was from Cameroon, Uganda, Mali, and Togo, respectively (Table 1 ). Most studies were conducted in urban tertiary public hospitals, university teaching hospitals, and rural and urban general hospitals, including primary care facilities operated by Non-Governmental Organizations (NGOs) for example in Mali [ 39 ]. Several validated tools assessed depression, anxiety, insomnia, stress, and PTSD (Table 1 ).

Table 1 provides an overview of the studies selected and validated instruments used to measure psychological disorders.

Table 2 provides comparisons with studies conducted outside of sub-Saharan Africa.

Table 3 provides information on studies showing the classification of psychological outcomes.

Table 4 are studies showing risk factors associated with psychological disorders.

Table 5 are studies that identified protective factors for psychological disorders.

Risks of bias and confounding factors

Most articles selected were cross-sectional studies that employed probability sampling procedures (Table 1 ). Cross-sectional study design minimized selection biases, but many used structured questionnaires, including online self-administered questionnaires, which increased bias due to social desirability. It was not clear how confounding variables were controlled in five papers reviewed [ 38 , 39 , 40 , 43 , 45 ] leading to excessive and perhaps inappropriate determination of associations.

Socio-demographic factors

In this review, the mean age of the respondents ranged between 23 and 35 years, and predominantly males. Age was associated with anxiety, and stress symptoms in 6(50%) of all the studies reviewed [ 35 , 37 , 40 , 41 , 42 , 44 ]. An age of over 40 years was associated with moderate to severe symptoms of PTSD. Two studies concluded that respondents aged over 40 years were more likely to develop PTSD symptoms than their younger counterparts [ 37 , 41 ].

Female gender was significantly associated with depression, anxiety, and stress symptoms among HCWs in seven studies reviewed [ 36 , 37 , 38 , 41 , 42 , 43 ]. Many studies found that being female, married, and a nurse were independent predictors of stress symptoms. Moreover, sex, age, marital status, type of profession, and working environment were significant factors for PTSD symptoms [ 37 , 41 ]. However, one study in Ethiopia found that the odds of depression were twice higher among male healthcare providers than among female healthcare providers [ 35 ].

Psychological impact on healthcare workers

Most studies reviewed directly assessed the prevalence of depression, anxiety, stress, insomnia, and PTSD in HCWs. Common causes of anxiety, fear, or psychological distress that health professionals reported were: lack of access to PPEs and other equipment, being exposed to COVID-19 at work and taking the infection home to their families, uncertainties that their organization will support/take care of their personal and family needs if they got infection, long working hours, death of colleagues, lack of social support, stigmatization, high rates of transmission and poor income [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. However, the prevalence of mental health symptoms exhibited great variations for example depressive symptoms were examined in nine studies [ 35 , 36 , 37 , 39 , 43 , 44 , 45 , 46 ], and varied between 16.3% and 71.9% among HCWs [ 38 , 39 ].

In addition, nine other studies reported high prevalence of anxiety symptoms among HCWs [ 35 , 36 , 37 , 40 , 43 , 44 , 45 , 46 , 47 ] which varied between 21.9% and 73.5% [ 36 , 39 ]. Five studies investigated HCWs' perceived stress during the pandemic; 15.5%-63.7% of HCWs reported high levels of work-related stress [ 35 , 36 , 37 , 43 , 45 ]. Three studies reported 12.4–77% of HCWs experienced sleep disturbances during the COVID-19 pandemic [ 37 , 39 , 40 ].

Post-traumatic stress disorder (PTSD) was in three studies [ 38 , 41 , 42 ], and the prevalence of PTSD-like symptoms varied between 51.6 and 56.8% in HCWs [ 38 , 41 ]. A qualitative study from Uganda reported high symptoms of depression, anxiety, and PTSD among HCWs [ 35 ]. Additionally, factors that increased the risk of PTSD symptoms were for example, working in emergency units and being frontline workers. Furthermore, many studies found that frontline HCWs had increased symptoms of mental disorders and being a frontline worker was an independent risk factor for depression, anxiety, and PTSD [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ].

Risk factors associated with adverse mental health outcomes

The qualitative study from Uganda reported the factors associated with mental disorder symptoms among HCWs. These were long working hours, lack of equipment (PPEs, testing kits), lack of sleep, exhaustion, high death rates, death of colleagues, and a high COVID-19 transmission rate among HCWs [ 35 ]. Lack of equipment (PPEs, ventilators, and testing kits), overworking, and lack of logistic support were in Ethiopian studies [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 45 ]. Most studies identified several risk factors for adverse mental health outcomes among respondents for example those with medical and mental illnesses, contacts with confirmed COVID-19 patients, and poor social support which were significantly associated with depression [ 42 , 43 ]. Other factors were females, nurses, married, frontline workers, ICU, emergency units, living alone, and lack of social support [ 35 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. Too, participants’ families with chronic illnesses, had contacts with confirmed COVID-19 cases, and poor social support were significantly associated with anxiety. Other risk factors associated with anxiety include exhaustion, long working hours, frontline workers, emergencies, nurses, pharmacists, laboratory technicians, married, older, younger, living alone, being female, working at general and referral hospitals, and perceived stigma. In addition, participants’ families with chronic illnesses, those who had contacts with confirmed COVID-19 cases, and those with poor social support were predictors of stress during the COVID-19 pandemic [ 37 , 38 , 40 , 41 , 42 , 43 , 45 ]. Other stress symptoms include having a medical illness, a mental illness, being a frontline worker, married, nurse, female, pharmacist, laboratory technician, physician, older age, lack of standardized PPE supply, low incomes, and living with a family [ 36 , 37 , 40 , 41 , 42 , 43 , 44 , 45 ]. Healthcare providers with low monthly incomes were significantly more likely to develop stress than those with high monthly incomes [ 38 ]. In addition, participants living alone, living with a family, and being married were associated with symptoms of psychological disorders among HCWs [ 36 , 37 , 38 , 45 ]. Overall, the risk factors for adverse psychological impacts are categorized in three thematic areas (i) occupational, (ii) psychosocial, and (iii) environmental aspects.

Occupational factors

Most studies showed that frontline HCWs, nurses, doctors, pharmacists, and laboratory technicians had significantly higher levels of mental health risks compared to non-frontline HCWs [ 35 , 36 , 37 , 38 , 40 , 42 , 43 , 45 ]. They experienced higher frequency of insomnia, anxiety, depression, and somatization than non-frontline medical HCWs. In contrast, Mali [ 39 ] and Cameroon [ 46 ] studies found a higher prevalence of depression, anxiety, and PTSD in non-frontline HCWs [ 39 , 46 ]. However, among HCWs, physicians were 20% less likely to develop mental health disorders than nurses, pharmacists, and laboratory technicians [ 39 ]. In addition, healthcare workers with low monthly incomes had higher symptoms of depression, anxiety, stress, and insomnia [ 37 ].

Healthcare groups

Five studies found that being a nurse was associated with worse mental disorders than doctors [ 36 , 37 , 40 , 44 , 45 ].

Frontline staff with direct contact with COVID-19

Most papers in the review found that being in a “frontline” position or having direct contact with COVID-19 patients was associated with higher level of psychological distress [ 35 , 36 , 37 , 38 , 40 , 42 , 43 , 45 ]. In addition, studies found that contact with COVID-19 patients was independently associated with an increased risk of sleep disturbances [ 40 , 46 ]. Moreover, HCWs who had contact with confirmed COVID-19 cases were more likely to develop depression, anxiety, and stress symptoms than those who had no contact with COVID-19 patients [ 36 , 37 , 38 , 43 , 45 ].

Lack of personal protective equipment (PPEs)

Most studies reported that the lack of PPEs was associated with higher symptoms of depression, anxiety, stress, and insomnia, while its availability was associated with fewer mental disorder symptoms [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ]. In Mali, workers from centres that provided facemasks were 51% less likely to suffer from depression, 62% less likely to develop anxiety, and 45% less likely to develop insomnia [ 39 ]. In Ethiopia, the odds of developing post-traumatic stress disorder were much higher among HCWs who did not receive standardized PPEs supplies than those who had [ 38 , 41 , 42 ]. In Uganda, the lack of PPEs was associated with depression, anxiety, and PTSD [ 35 ].

Heavy workload

Longer working hours, increased work intensity, increased patient load, and exhaustion were risk factors in Ugandan [ 35 ] and Ethiopian studies [ 36 ].

Psychosocial factors: perceived stigma and fear of infection

The fear of infection was in the qualitative study from Uganda [ 35 ], one quantitative study from Cameroon [ 47 ] and seven cross-sectional studies from Ethiopia [ 36 , 37 , 38 , 41 , 42 , 43 , 44 ]. Poor social support was associated with PTSD symptoms, depression, anxiety, and stress [ 35 , 36 , 37 , 38 , 42 , 43 ]. Two studies reported that HCWs with perceived stigmatization were more likely to suffer from depression, anxiety, stress, and PTSD [ 37 , 42 ].

family concerns

This came up as one of the main risk factors of stress in almost all studies, especially among those HCWs in direct contact with confirmed COVID-19 cases [ 35 , 36 , 37 , 38 , 40 , 41 , 42 , 43 , 44 , 45 ]. A family member suffering from COVID-19 was associated with poor mental health outcomes in HCWs [ 36 , 37 ].

Protective psychosocial factors

Two studies suggest a reduction of perceived stigma can be achieved by sensitization of communities about COVID-19 [ 37 , 42 ], and four studies recommend solid social support [ 36 , 37 , 42 , 43 ].

Safety of family

Family safety had the most significant impact in reducing stress. Safety from COVID-19 infection and financial protection of families were essential coping strategies for HCWs [ 35 , 36 ].

Underlying illnesses

We found three studies that reported an underlying medical and mental illness as an independent risk factor for poor psychological outcomes [ 42 , 43 , 45 ].

Protective factors against adverse mental health outcomes

The review identified protective factors to adverse mental health outcomes during COVID-19. The qualitative study from Uganda and four quantitative cross-sectional studies from Ethiopia identified some protective factors [ 35 , 38 , 41 , 42 , 45 ]. The protective factors are grouped under three thematic areas (i) occupational, (ii) psychosocial, and (iii) environmental aspects.

The qualitative study identified many social coping strategies among respondents, including family networks, community networks, help from family, responsibility to society, assistance from community members, availability of assistance from strangers, and the symbiotic nature of assistance in the community [ 35 ].

Protective occupational factors

Studies suggest that physicians suffered fewer mental health disorders partly because of their experience with previous epidemics [ 37 , 42 , 45 ].

Some necessary coping measures include good hospital guidance and ongoing training of frontline HCWs [ 37 , 42 , 45 ].

Adequate supply of PPEs

As mentioned above, PPE was a protective factor when adequate and a risk factor for poor mental health outcomes when deemed inadequate [ 35 , 36 , 37 , 42 , 43 ].

The COVID-19 pandemic has been an ongoing global public health emergency that has burdened healthcare workers' physical and mental well-being (HCWs) [ 1 , 5 ]. Our review confirms the enormous magnitude of mental health impact of COVID-19 on healthcare workers in sub-Saharan Africa, and it is widespread, with significant levels of depression, anxiety, distress, and insomnia; especially those working directly with COVID-19 patients at particular risk [ 34 , 35 , 36 , 37 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. Out of the twelve articles reviewed, eight studies (66%) came from Ethiopia, and this has implications on the results (Table 1 ). This finding indicates few research published to date on the psychological impact of the pandemic on the mental health of HCWs in sub-Saharan Africa; a subregion that the COVID-19 pandemic has severely impacted.

Overview of the study sites

Studies in this review were conducted predominantly in hospital settings. We found only one study relating to primary healthcare workers or facilities [ 38 ]. This finding is of concern, as there is increasing evidence that many non-frontline HCWs continue to suffer psychological symptoms long after the conclusion of infectious disease epidemics [ 7 , 8 ]. In addition, a significant mortality due to COVID-19 was due to excess morbidity, some of which were from primary care facilities. Given that this study is the first narrative review in sub-Saharan Africa, it would be helpful to briefly compare our findings with some published reviews and surveys from other regions (Table 2 ).

High prevalence of psychological disorders among participants

Investigators in this review found 16.3–71.9% HCWs with depressive symptoms, 21.9–73.5% had anxiety symptoms, 15.5–63.7% experienced work-related stress symptoms, 12.4–77% experienced sleep disturbances, and 51.6–56.8% PTSD symptoms [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. This high prevalence of mental health symptoms among HCWs in our review is consistent with previous reviews conducted early in the pandemic in sub-Saharan Africa [ 31 ], Asia [ 17 , 18 , 26 , 28 ], USA & Europe [ 15 , 16 ], and supported by a batch of cross-sectional studies globally [ 11 , 12 , 13 , 14 , 19 , 27 , 30 ]. We found mixed results with significant variations within and among regions and countries, as depicted in Tables 1 and 2 .

Risk factors of psychological disorders among participants

Studies established that HCWs responding to the COVID-19 pandemic in sub-Saharan Africa were exposed to long working hours, overworking, exhaustion, high risk of infection, and shortage of personal protective equipment (Tables 3 and 4 ). In addition, HCWs had deep fear, were anxious and stressed with the high transmission rate of the virus among themselves, high death rates among themselves and their patients, and lived under constant fear of infecting themselves and their families with obvious consequences [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. Some HCWs were deeply worried about the lack of standardized PPEs, known treatments and vaccines to protect against the virus. Many health workers had financial problems, lacked support from families and employers if they contracted the virus [ 34 , 35 , 36 , 37 , 39 , 40 , 41 , 42 , 44 ]. An additional source of fear and anxiety was the perceived stigma attached to being infected with COVID-19 by the public [ 36 , 41 ]. Studies found that HCWs, especially those working in emergency, intensive care units, infectious disease wards, pharmacies, and laboratories, were at higher risk of developing adverse mental health impacts compared to others [ 34 , 35 , 36 , 37 , 39 , 40 , 41 , 42 , 43 , 44 ]. This is supported by previous reviews [ 15 , 16 , 17 , 18 , 26 , 28 ] and cross-sectional studies [ 10 , 11 , 12 , 13 , 14 , 20 , 21 , 23 , 25 , 30 ]. However, findings were inconsistent on the impact of COVID-19 on frontline health workers, with ten studies [ 35 , 36 , 37 , 39 , 40 , 41 , 42 , 44 , 45 ] suggesting they are at higher risk than peers and two studies showing no significant difference in psychological disorders relating to the departments [ 38 , 43 ].

The Mali’s study was conducted exclusively in primary care facilities among HCWs not involved in treating COVID-19 cases but still registered a very high prevalence of depression 71.9%, anxiety 73.6%, and insomnia 77.0% [ 39 ]. In contrast, two studies conducted among HCWs at COVID-19 treatment facilities in Ethiopia [ 36 , 38 ] registered much lower prevalence of depression 20.2%, anxiety 21.0%, and insomnia12.4% [ 36 ], and 16.3%, 30.7% and 15.9% respectively, in the second study [ 38 ]. These findings show that not only frontline HCWs experienced mental health disorders during this pandemic but highlight the need for direct interventions for all HCWs regardless of occupation or workstation during this and future pandemics. The significant disparity in the studies could be due to structural, occupational, and environmental issues for example challenges faced by Mali's healthcare systems, characterized by acute equipment shortages, lack of PPEs, human resources, lack of trained and experienced HCWs, ongoing nationwide insecurity, and terrorism compared to Ethiopia. Therefore, local context needs to be considered as contributing factor to mental health disorders among HCWs.

Regional variations of psychological disorders

Tan et al . found a higher prevalence of anxiety among non-medical HCWs in Singapore [ 27 ]. As previously noted, the prevalence of poor psychological outcomes varied between countries. Compared to sub-Saharan Africa and China, data from India [ 23 ] and Singapore [ 27 ] revealed an overall lower prevalence of anxiety and depression than similar cross-sectional data from sub-Saharan Africa [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ] and China [ 9 , 25 , 30 ]. This finding suggests that different contexts and cultures may reveal different psychological findings and that, it is possible that being at different countries’ outbreak curve may play a part, as there is evidence that it is influential.

Tan et al . suggests that medical HCWs in Singapore had experienced a SARS outbreak and thus were well prepared for COVID-19 psychologically and infection control measures [ 27 ]. What can be deduced is that context and cultural factors play a role, not just the cadre or role of healthcare workers [ 16 ]. It also highlights the importance of reviewing evidence regularly as more data emerge from other countries.

One hospital in Ethiopia found that the thought of resignation was associated with higher chances of mental health disorders and that pharmacists and laboratory technicians who did not receive prior training exhibited higher symptoms of mental health disorders compared to others [ 36 ]. Work shift arrangement, considering a dangerous atmosphere presented by working in COVID-19 wards, was one which exacerbated or relieved mental health symptoms among HCWs, with shorter exposure periods being most beneficial [ 36 ]. Meanwhile, studies found that financial worries caused by severe lockdowns and erratic payment of salaries and allowances were also major stressors [ 35 ]. This finding is like studies in Pakistan [ 13 ] and China [ 30 , 32 ].

In this review, HCWs who had contact with confirmed COVID-19 patients were more affected by depression, anxiety, and stress than their counterparts who had not [ 35 , 36 , 37 , 40 , 41 , 43 , 45 ]. This finding is like previous reviews [ 15 , 16 , 17 , 18 , 26 , 28 , 31 ] and cross-sectional studies [ 9 , 10 , 11 , 12 , 13 , 14 , 21 , 23 , 24 , 25 , 27 , 30 ], which reported higher depression, anxiety, and psychological symptoms of distress in HCWs who were in direct contact with confirmed or suspected COVID-19 patients.

A study in Pakistan showed that 80% of participants expected the provision of PPE from authority [ 13 ], and 86% were anxious. Some respondents alluded to forced deployment, while in Mali, 73.3% were anxious, with the majority worrying about the shortage of nurses [ 39 ]. Therefore, prospects of being deployed at a workstation where one had not been trained or oriented contributed to fear among health workers. In the sub-Saharan African context, this scenario can best be represented in HCWs involved in internship who must endure hard work during their training. Tan et al . found that junior doctors were more stressed than nurses in Singapore [ 27 ].

Socio-demographic characteristics

Nearly all studies in our review suggest that socio-demographic variables for example age, gender, marital status, and living alone or with families contribute to the high mental disorder symptoms [ 35 , 36 , 37 , 39 , 40 , 41 , 42 , 43 , 44 ]. We, the authors suggest that these observations are handled cautiously as several investigators of these reviewed articles did not entirely control the influence of confounding variables. An alternative explanation for this study's findings may be the more significant risks of frontline exposure amongst women and junior HCWs, predominantly employed in lower-status roles, many of whom lacked experience and appropriate training within healthcare system globally. It is also important to note that respondents to all studies, when disaggregated by gender, and age, were predominantly younger or female, which may have impacted the outcomes of these findings [ 16 ]. In addition, the consistently higher mortality rates, and risk of severe COVID-19 disease amongst men would suggest that the complete picture regarding gender and mental health during this pandemic is still incomplete [ 16 ]. Moreover, in several studies, both younger and older age groups were equally affected by mental health symptoms but for different reasons. Cai et al . [ 32 ] in a Chinese study on HCWs for example observed that irrespective of age, colleagues' safety, self and families' safety, the lack of treatment for COVID-19 was a factor that induced stress in HCWs. Similarly, in our review, the lack of PPEs, high infection transmission rates, high death rates among HCWs, and the fear of infecting their families were the factors that induced stress in all HCWs [ 34 , 35 , 36 , 37 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ].

We, the authors propose that paying close attention to concerns of HCWs by employers would greatly relieve some stressors and contribute to increased mental well-being of participants. Compared with physicians, our review showed that nurses were more likely to suffer from depression, anxiety, insomnia, PTSD, and stress [ 35 , 37 , 39 , 40 , 41 , 44 , 45 ]. Workloads and night shifts in healthcare facilities, as well as contacts with risky patients, enhanced nurses' mental distress risks [ 15 , 16 , 17 , 18 , 26 , 27 , 28 ]. In addition, nursing staff have more extended physical contacts and closer interactions with patients than other professionals, providing round-the-clock care required by patients with COVID-19 and thus the increased risk [ 15 ]. On the one hand, we posit that most senior physicians are experienced and always keep well-informed with emerging medical emergencies. The majority become aware of emerging epidemic early and actively protect themselves from infections through regular scientific literature updates compared to their junior counterparts. Senior physicians also spend less time in emergency wards unless there is a need to conduct specific procedures which cannot be undertaken by senior housemen or general medical officers. Cai et al . [ 32 ] concluded that it is essential to have a high level of training and professional experience for healthcare workers engaging in public health emergencies, especially for the new staff. As a result, these findings highlight the importance of focusing on all the frontline HCWs sacrificing to contain the COVID-19 pandemic.

Regular monitoring of high-risk groups

There is a need to continue monitoring the high-at-risk groups, including nursing staff, interns, support staff, and all deployed in emergency wards. These high-at-risk groups should be encouraged to undertake screening, treatment, and vaccination to avoid the medium and long-term consequences of such epidemics [ 15 , 16 , 35 , 37 , 40 , 44 ].

Social support and coping mechanisms

The effect of social support and coping measures is in the qualitative study [ 34 ] and three other quantitative studies [ 36 , 41 , 42 ] which concluded that respondents with good social support were less likely to suffer from severe depression, anxiety, work-related stress, and PTSD. The qualitative study identified several coping measures, including community and organizational support, family, and community networks, help from family, responsibility to society, and assistance from community members and strangers, including the symbiotic nature of assistance in the community [ 35 ]. Other measures include providing accommodation and food to employees [ 35 ].

Interestingly, no study examined the association of resilience and self-efficacy with sleep quality, degrees of anxiety, depression, PTSD, and stress. However, a Chinese study by Cai et al. [ 32 ] suggests that the social support given to HCWs causes a reduction in anxiety and stress levels and increases their self-efficacy. In divergence, Xiao et al . [ 46 ] found no relationship between social support and sleep quality.

Only two studies in our review examined the effects of stigma on the mental health of HCWs [ 36 , 41 ] and found that HCWs with perceived stigma were more likely to be depressed, anxious, stressed, and prone to poor sleep quality [ 36 , 41 ]. We, the authors suggest that better community sensitization by creating public awareness involving appropriate local community structures and networks are essential. The broader community in sub-Saharan Africa may have suffered severely from infodemics with severe consequences on their mental health, especially during the difficult lockdowns. In addition, removing discrimination/inequalities at the workplace based on race and other social standings have a powerful influence on the mental health outcomes of HCWs. Also, because emotional exhaustion is long associated with depression, anxiety, and sleep disturbances, none of the studies in our review examined burnout as an essential component of mental health disorders in HCWs in sub-Saharan Africa.

Protective and coping measures

In this review we have provided evidence about personal, occupational, and environmental factors that were important protective and coping measures against psychological disorders. Based on these factors we suggest some protective and coping measures which can help to reduce the negative effects of the pandemic on mental health of HCWs in sub-Saharan Africa. Organizations and healthcare managers need to be aware that primary prevention is key to any successful interventions to contain and control any epidemic. This should take the form of planned regular training, orientation and continuing medical education grounded on proven infection control measures. These measures need to be backed up by timely provision of protective equipment, drugs, testing facilities, vaccines, isolation facilities, clinical and mental health support, and personal welfare of HCWs [ 35 , 36 , 37 , 42 , 45 ]. The effect of community and organizational support and coping measures was shown by the qualitative study [ 35 ] and five other quantitative studies [ 36 , 37 , 41 , 42 , 43 ] indicating that respondents who had good social and organizational support were less likely to suffer from severe depression, anxiety, work related stress and PTSD. Prior experience with comparable pandemics and training are suggested as beneficial coping strategies for healthcare workers during this pandemic but also local social structural and geopolitical conditions appear to determine the pattern and evolution of mental health symptoms among HCWs [ 14 , 15 , 31 , 32 , 47 ]. In our case the high prevalence of all mental health symptoms in non-frontline primary health care facilities in Mali [ 39 ] which was already plagued with instability and weak healthcare systems prior to the pandemic is a case in point. Results are particularly consistent in showing that provision of PPEs, testing kits, orientation training of workers, work shift arrangements, provision of online counselling, provision of food and accommodation and prompt payment of allowances by employers were important protective measures [ 35 , 36 , 37 , 38 , 39 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. The feeling of being protected is associated with higher work motivation with implication for staff turnover [ 35 , 38 , 43 , 45 ]. Hence, physical protective materials [ 14 ], together with frequent provision of information, should be the cornerstone of any interventions to prevent deterioration in mental health of HCWs (Table 5 ). Finally, provision of rest rooms, online consultation with psychologists/psychiatrists, protection from financial hardships, access to social amenities and religious activities are some important coping measures [ 35 , 36 , 38 , 42 , 45 ]. In this era of digital health care with plentiful internet and smartphones, organization can conduct online trainings, online mental health education, online psychological counselling services, and online psychological self-help intervention tailored to the needs of their HCWs [ 35 , 37 , 42 ]. In addition, it is essential to understand and address the sources of anxiety among healthcare professionals during this COVID-19 pandemic, as this has been one of the most experienced mental health symptoms [ 48 ]. Adequate protective equipment provided by health facilities is one of the most important motivational factors for encouraging continuation of work in future outbreaks. Furthermore, availability of strict infection control guidelines, specialized equipment, recognition of their efforts by facility management, government, and reduction in reported cases of COVID-19 provide psychological benefits [ 15 , 32 ]. Finally, we call upon Governments (the largest employers of HCWs) in sub-Saharan Africa to do what it takes to improve investments in the mental health of HCWs and plan proactively in anticipation of managing infectious disease epidemics, including other expected and unexpected disasters.

Future research direction

There was no study that examined the association of resilience and self-efficacy with sleep quality, degrees of anxiety, depression, PTSD, and stress. Although emotional exhaustion has long been associated with depression, anxiety, and sleep disturbances, no study in our review examined burnout as an important component of mental health disorders in HCWs in sub-Saharan Africa. The impacts of infodemics, stringent lockdown measures, discrimination/inequalities at workplaces based on race, and other social standings on mental health outcomes of HCWs need to be investigated.

Future studies are needed on the above including other critical areas like suicidality, suicidal ideations, and substance abuse during the COVID-19 pandemic. In addition, there is a significant variation of related literature calling for more rigorous research in future. More systematic studies will be required to clarify the full impact of the pandemic so that meaningful interventions can be planned and executed at institutional and national levels in the Sub-Saharan Africa.

Limitations of this study

There are some limitations to this study. First, most of the studies are from one country, limiting the generalizability of the results to the whole African continent. Second, all the studies were cross-sectional and only looked at associations and correlations. There is a need for prospective or retrospective cohort or case–control studies on this subject matter. Longitudinal research studies on the prevalence of mental disorders in the COVID-19 pandemic in the sub-Saharan Africa are urgently required. Third, most studies reviewed did not adequately examine protective factors or coping measures of the health workers in their settings. In addition, most studies did not pay strict attention to confounding variables which could have led to inappropriate results and conclusions. Fourth, most sample sizes were small and unlikely representative of the population and yet larger sample sizes would better identify the extent of mental health problems among health workers in the region. Fifth, depression, anxiety, and stress were assessed solely through self-administered questionnaires rather than face-to-face psychiatric interviews. Sixth, these studies employed various instruments and different cut-off thresholds to assess severity. Notably, the magnitude and severity of reported mental health outcomes may vary based on the validity and sensitivity of the measurement tools. Seventh, there was no mention of mental baseline information among the studied population and therefore it was unknown if the studied population had pre-existing mental health illnesses that decompensated during the pandemic crisis. Eight, investigators did not give much attention to stigma, burnout, resilience, and self-efficacy among study participants.

Furthermore, our review did not employ systematic reviews or meta-analyses methods for the information generated. This narrative review paper precluded deeper insight into the quality of reviewed articles for this paper. Still, our observation was that investigators did not consider the strict lockdown measures, quarantine, and isolation imposed by many countries in sub-Saharan Africa as possible risk factors for mental health disorders among HCWs.

Based on the articles reviewed, the prevalence of depression, anxiety, insomnia, and PTSD in HCWs in the sub-Saharan Africa during the COVID-19 pandemic is high. We implore health authorities to consider setting up permanent multidisciplinary mental health teams at regional and national levels to deal with mental health issues and provide psychological support to patients and HCWs, always supported with sufficient budgetary allocations.

Long-term surveillance is essential to keep track of insidiously rising mental health crises among community members. There is a significant variation of related literature thus calling for more rigorous research in the future. More systematic studies will be needed to clarify the full impact of the pandemic so that meaningful interventions can be planned better and executed at institutional and national levels in sub-Saharan Africa.

Availability of data and materials

Datasets analysed in the current study are available from the corresponding author at a reasonable request.

Abbreviations

Coronavirus disease 2019

Healthcare workers.

Mental health

Public health emergency

Personal protective equipment

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We thank Uganda Medical Association Acholi-branch members for the financial assistance which enabled the team to conduct this study successfully.

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Freddy Wathum Drinkwater Oyat, Johnson Nyeko Oloya, Pamela Atim, Judith Aloyo & David Lagoro Kitara

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Oyat, F.W.D., Oloya, J.N., Atim, P. et al. The psychological impact, risk factors and coping strategies to COVID-19 pandemic on healthcare workers in the sub-Saharan Africa: a narrative review of existing literature. BMC Psychol 10 , 284 (2022). https://doi.org/10.1186/s40359-022-00998-z

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Obstructive sleep apnea and acute lower respiratory tract infections: a narrative literature review.

1. Introduction

2. literature search strategy, 3. obstructive sleep apnea and community-acquired pneumonia, 4. obstructive sleep apnea and influenza pneumonia, 5. obstructive sleep apnea and covid-19 pneumonia, 6. obstructive sleep apnea and lower respiratory tract infections: pathophysiology, 6.1. altered immunity, 6.2. risk of aspiration, 6.3. the role of obesity and other comorbidities, 7. obstructive sleep apnea and lower respiratory tract infections: treatment, 7.1. settings of care and empiric antibiotics, 7.2. specific risks guiding empiric antibiotic therapy, 7.3. antibiotic pharmacokinetics, side effects, and resistance, 8. discussion, 9. conclusions, supplementary materials, author contributions, institutional review board statement, informed consent statement, data availability statement, acknowledgments, conflicts of interest.

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Nemet, M.; Vukoja, M. Obstructive Sleep Apnea and Acute Lower Respiratory Tract Infections: A Narrative Literature Review. Antibiotics 2024 , 13 , 532. https://doi.org/10.3390/antibiotics13060532

Nemet M, Vukoja M. Obstructive Sleep Apnea and Acute Lower Respiratory Tract Infections: A Narrative Literature Review. Antibiotics . 2024; 13(6):532. https://doi.org/10.3390/antibiotics13060532

Nemet, Marko, and Marija Vukoja. 2024. "Obstructive Sleep Apnea and Acute Lower Respiratory Tract Infections: A Narrative Literature Review" Antibiotics 13, no. 6: 532. https://doi.org/10.3390/antibiotics13060532

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Politics and Literature at the Dawn of World War II

If a single image can stand for Ernest Hemingway’s For Whom the Bell Tolls , it is the one that begins and ends the novel: the American guerrilla fighter Robert Jordan prone on the pine-needled floor of a forest near Segovia, awaiting the appearance of enemy soldiers. If the novel has a sound, it is the roar of the fascist bombers flying low over the guerrillas’ cave. If the novel has a flavor, it’s that of the “bitter, tongue-numbing, brain-warming, stomach-warming, idea-changing” absinthe Jordan has smuggled in a leather flask from his previous life. And if the novel has a smell, it’s the smell of death. Not the smell of putrefaction, though the novel is littered with rotting corpses. It is the smell of a death foretold: the odor given off by a person, like Robert Jordan, who knows he will soon die.

Jordan himself refuses to believe such sorcery when he hears of it from Pilar, the guerrilla band’s matriarch. He demands that Pilar describe this alleged stench of preordained death in precise terms. The first element of it, she tells him, “is the smell that comes when, on a ship, there is a storm and the portholes are closed up.” Another note can be tasted by kissing the mouth of an old woman in Madrid who, in the predawn fog, descends upon the slaughterhouse to drink the blood of the murdered beasts. Add to this the odor of dead chrysanthemums. The final component is the reek of a brothel, which Pilar describes in a lengthy speech of unapologetic precision, ending with an invitation to “wrap this sack around thy head and try to breathe through it.” Combine all that and you have, finally, the smell of a death foretold.

You also have something that you won’t find in any history of the Spanish Civil War. In Politics and Literature at the Dawn of World War II , the Dartmouth literary scholar James A.W. Heffernan proposes that academic and popular histories, diaries, and journalistic accounts offer only a blinkered view of the past. For a fuller understanding of any historical period, you must read the literature it produced. Best of all, you must read the literature that was written and published while the events of the period were still unfolding.

“Punctual literature,” as Heffernan calls it, is a narrow category, especially when it comes to World War II, for practical reasons: it isn’t easy to write and publish while being bombed. To fortify his argument Heffernan further narrows his definition of “punctual,” limiting his survey primarily to fiction, poetry, and plays set or composed or published in 1939 (which happens to be, he gallantly declines to mention, the year of his birth) “and one or at most two of the years that followed.” Virginia Woolf’s Between the Acts , Patrick Hamilton’s Hangover Square , and Evelyn Waugh’s Put Out More Flags are novels about historical events, but they’re not historical fiction, strictly speaking, because they were written in the early years of the war, before the conclusion was known—before the chaos of those years could be sealed and wrapped and ribboned in a tidy narrative. “The uncertainty of being in medias res ,” writes Heffernan, “is precisely what punctual literature aims to represent.” Ignorance of the war’s outcome does not count as a deficiency of this literature, as it might to a historian, but as an advantage.

Here Heffernan risks stating the obvious. Of course Hemingway’s novel produces a very different account of the Spanish Civil War than what can be found, for instance, in Antony Beevor’s The Battle for Spain . Most readers of Irène Némirovsky’s Suite française will feel no compulsion to fact-check its account of the exodus from Paris against Julian Jackson’s The Fall of France (2003). Hemingway made this point himself, in his introduction to Men at War (1942):

A writer’s job is to tell the truth. His standard of fidelity to the truth should be so high that his invention, out of his experience, should produce a truer account than anything factual can be.

Heffernan calls this argument “startling,” but it is fundamental to fiction. Facts tell us little or nothing about the experience of an age, for experience resides in the minds of those who lived it. Beevor’s book tells how the war was won. Hemingway’s novel tells us “how the war felt ,” or at least how it felt to one volunteer fighter.

Heffernan must therefore take a more daring approach. He directs his argument not to readers of literature but to historians. Brazenly he trespasses into their territory, their cleared jungles and straightened rivers, as an emissary from the shadowy realm of make-believe who dares to suggest that their scrupulous volumes, no matter how impressively researched or dramatically written, cannot match the honesty of fiction, poetry, or theater. “Histories tell us much…about the origins of World War II,” he writes. “But the literary works…examined in this book tell us even more.”

These are fighting words. Heffernan’s method is to pit a work of literature against a definitive historical account of the same subject. In these head-to-head battles, literature cheerfully concedes some predictable defeats. No reader of Hemingway will learn, for instance, that the Segovia Offensive was ordered by Indalecio Prieto Tuero, Spain’s minister of defense, in order to forestall the Nationalists’ assault on Bilbao. Readers of Bertolt Brecht’s “The Necessity of Propaganda,” collected in the Svendborg Poems , can be forgiven if they don’t realize that the word “program” should be read as an allusion to the twenty-five-point Program of the National Socialist German Workers’ Party that Hitler proclaimed in his February 24, 1920, speech at Munich’s Hofbräuhaus. History claims such empty victories as these, but in Heffernan’s book, literature wins the war.

An ideal candidate for this type of analysis is Martha Gellhorn’s A Stricken Field (1940), a novel written by an American reporter in Czechoslovakia about the experiences of an American reporter in Czechoslovakia. It is, Heffernan writes, “the work of a journalist who discovered, paradoxically, that fiction alone could re-create the truth of what she had seen.” We have here a clean test case, with Gellhorn’s journalism serving as the control. She spent several weeks in and around Prague on assignment for Collier’s during the fall of 1938, shortly after Hitler annexed the Sudetenland—the predominantly German-speaking part of the country—for a report titled “Obituary of a Democracy.” The same research forms the basis of A Stricken Field .

What truth does the novelist Gellhorn record that the journalist Gellhorn cannot? She renders the lives of her subjects in far richer detail, though this may say more about the editorial conventions of Collier’s than narrative journalism as a form. In her fiction, Gellhorn writes about the novelists and journalists who came to Prague to exploit the situation for their careers, offering a behind-the-scenes perspective that Collier’s editors might have considered unseemly. And through her surrogate, a reporter named Mary Douglas, Gellhorn writes about herself—her own vulnerabilities and cynicism and bystander guilt. When a young Czech Communist in hiding begs Douglas to condemn the Nazis for her American audience, she dutifully obliges, but without conviction: “After they had public opinion all properly shaped, what good did it do? It was immensely easy to make people hate but it was almost impossible to make them help.” Ultimately Douglas decides to engage, intervening in the lives of several people she meets through her reporting. She brings one injured man to a hospital and smuggles out documents for another—a haphazard, largely ineffectual response to her feelings of impotency, but the only one available to her.

For Heffernan the novel’s most impressive accomplishment, however, is Gellhorn’s depiction of Czech cruelty. Like Hemingway, whom she would soon marry, Gellhorn felt it was her duty, when writing for a large public readership, to lie in service of the virtuous side—to propagandize, in other words. (When Hemingway wrote that “a writer’s job is to tell the truth,” he meant a writer of fiction; in his journalism he was a devoted propagandist, careful to suppress any facts that “could hurt the Republic,” as he acknowledged in correspondence.) Although Gellhorn and Hemingway witnessed what he called a “carnival of treachery on both sides” during the Spanish Civil War, they reserved their accounts of Republican barbarity for their novels. The most frightening scene in For Whom the Bell Tolls describes the rabid executions of Loyalists in a small hilltop town by a Republican mob who torture their victims and defile their corpses before tossing them into a gorge. Gellhorn saved her Republican horror stories for A Stricken Field , which she told friends was the book she had wanted to write about the Spanish Civil War and the Republicans’ betrayal of their ideals. But to do so she had to transpose the narrative to Czechoslovakia.

She managed easily enough, for the Czech authorities treated the most vulnerable among them almost as savagely as the Spanish Republicans treated fascist prisoners of war. In A Stricken Field , Gellhorn describes how German refugees—hundreds of thousands of Sudeten Germans who had rejected the Nazi Party—were routinely sent back across the border, ensuring their imprisonment, and in some cases their execution, for treason.

Gellhorn doesn’t mention any of this in Collier’s . She does tell the story of one refugee family forced to return to the occupied village they had fled, but she neglects to say who sent them back, or why. In her novel she fills in these details, most brutally in an episode about a refugee who, after being hit by a car, is so terrified of encountering the Czech police that he refuses medical care. But an officer appears nevertheless and orders the refugee to the police station, where he will be condemned to return to Nazi territory.

As Heffernan is careful to point out, Gellhorn’s fictional account of Hitler’s annexation has its own omissions and blind spots. She ignores almost entirely, for instance, the plight of the people who suffered most gruesomely at the hands of the Czech authorities: the Jews. Némirovsky’s disinterest in Jewish anguish is even more conspicuous in Suite française , given her history of employing antisemitic flourishes in her fiction—a habit that drew attacks in her own lifetime and attracted greater controversy after the novel was discovered and published to enormous success in 2004.

But the near-total absence of Jewish characters in Suite française is as much an aesthetic blunder as a moral one. The story of Némirovsky’s own efforts to secure protection from Vichy France would have neatly complemented the narratives of vanity and self-delusion that define the novel. In September 1940, a month before the Vichy government decreed that “foreign residents of Jewish descent may be interned in special camps,” Némirovsky wrote a letter of appeal directly to Marshal Pétain. She touted her longtime association with the conservative periodical Revue des Deux Mondes and her personal connections to various enthusiastic supporters of his collaborationism. She boasted of her refusal to concern herself with politics and of having dedicated herself to writing literary works in which she had “tried [my] best to make France well-known and well-liked.” Even after her deportation, her husband, Michel Epstein, shortly before his own murder, appealed to the German ambassador: “Even though my wife is of Jewish descent, she does not speak of the Jews with any affection.” Neither Pétain nor any of Némirovsky’s collaborationist friends came to her aid, and she died of typhus in Auschwitz. *

Such fickleness of authorial attention, even unthinking bias, is critical to Heffernan’s argument. Punctual literature is proudly piecemeal and defiantly subjective. It offers us the perspective of the soldier, not the secretary of defense; of the random bystander, not the chancellor. Free of the historian’s imperative to write an authoritative, objective account, punctual literature instead records the effects of a particular event or age on “a mind capable of calibrating its significance at the time it occurred .” Or minds , for it is not only the author but his or her characters whose lives are deranged by the cataclysms of their age. Any single person’s experience of a grand historical transformation can only be uncertain, idiosyncratic, contradictory. How, for instance, does one make sense of killing strangers in war, even for a virtuous cause? In For Whom the Bell Tolls , such inquiries inspire Robert Jordan’s self-tormenting interior dialogues, which convulse him without warning:

How many is that you have killed? he asked himself. I don’t know. Do you think you have a right to kill any one? No. But I have to. How many of those you have killed have been real fascists? Very few. But they are all the enemy to whose force we are opposing force. But you like the people of Navarra better than those of any other part of Spain. Yes. And you kill them. Yes…. Don’t you know it is wrong to kill? Yes. But you do it? Yes. And you still believe absolutely that your cause is right? Yes.

Hemingway offers no synthesis, no answer, no satisfaction—only the questioning, and the questioning of the questioning.

Some wartime minds are not so sensitive. Basil Seal, Evelyn Waugh’s recurrent amoral dandy, would not be able to listen to Robert Jordan’s musings about war as a crusade on behalf of “all of the oppressed of the world” without snickering into his gin. In Put Out More Flags , war is just another racket, the latest opportunity for shameless self-promotion, blackmail, giggles, and social gamesmanship. As one character says, “One takes one’s gas-mask to one’s office but not to one’s club.”

Waugh did not write autobiographically: none of his characters is a Waugh stand-in, despite sharing his class and milieu. Waugh, in fact, committed himself to the war effort with much greater seriousness than any member of Basil Seal’s coterie, joining the Royal Marines as a second lieutenant. It would be tempting to say that Put Out More Flags reflected Waugh’s own disillusionment about the honor of war, but as Heffernan points out, he was under no illusions when he enlisted. Waugh’s correspondence from the period reflects a frank expectation of his own violent death and describes the fighting as “tedious & futile & fatiguing.” (In this way Waugh resembles Robert Jordan more than Basil Seal, risking his life for a cause that disgusted as much as inspired him.) In diary entries from the Battle of Crete, during which the British and their allies suffered a humiliating defeat, Waugh describes starving men reduced to ghosts, crawling out of ditches like lizards. He began writing Put Out More Flags on an ocean liner back home. He would later claim it was the only book he wrote purely for pleasure. John Keegan, the preeminent military historian of the period, called Waugh’s farce of pompous dodgers and profiteers “the greatest English novel of the Second World War.”

If war, in Waugh, is an opportunity for self-aggrandizement, in Henry Green’s Caught it is an excuse to sleep around. War is sexual opportunity, an aphrodisiac, and an excuse for the suspension of shame and inhibition. “War,” as one character puts it, “is sex.”

Caught is the strangled tale of Richard Roe, a patrician businessman who volunteers as an auxiliary fireman in London during the first year of the war (following the example of his pseudonymous author, who was born Henry Vincent Yorke). As in Put Out More Flags , the action is mainly set during the so-called phony war, the eight-month period between the British and French declaration of war and the German invasion of France and the Low Countries, during which the Allies engaged in little actual fighting. These months of playing soldier allow Roe to relish the perks of wartime footing without the risk of being slaughtered. He leaves behind his irksomely affectionate wife and his mystifying young child at their staid country estate to go slumming with firemen in London. There he enjoys the easy camaraderie of the fire station, the delusion of valor, and the long expanses of free time, which inexorably draw him to lonely working-class women.

There is an unpleasant tincture to Roe’s idyll, however. His boss, Albert Pye, has a personal connection to the recent, if brief, abduction of Roe’s son, Christopher. Before the war, while visiting a toy store with his nanny, Christopher was lured by an eccentric woman to her apartment, where he was abandoned and later found by police. So it is with some awkwardness that Roe discovers that Pye is the brother of his son’s abductor. Worse, Pye partially blames Roe for the cruel (and expensive) treatment his sister has received since her institutionalization. But the force of war—the thrill of war—sweeps aside these interpersonal tensions with relative ease, the resentments blanched by the enthusiastic preparations for bombs and broads. It is only once the sky lights on fire that Roe realizes the whole endeavor has been a sham. Their year of training vaporizes as the “mile-high pandemonium of flame” descends upon the incompetent and overwhelmed auxiliary firemen, who flee in panic. Roe returns to his estate traumatized by war and even less capable of negotiating the most fundamental duties of marriage and fatherhood.

The aphrodisiac qualities of war, the class tensions, and the incommunicability of the wartime experience to outsiders—all of these have been observed, Heffernan acknowledges, in nonfiction accounts of the Blitz. (“Sexual desire, especially in women, was much intensified,” says a psychoanalyst in Juliet Gardiner’s 2011 book The Blitz: The British Under Attack , Heffernan’s historical counterweight to Caught .) Green’s unique accomplishment, then, is to convey “a richer quality of truth: a truth embracing the whole lives—physical, social, familial, emotional, sexual, and psychological—of men and women caught up in the blitz.” This is undeniable, but it’s hardly categorical evidence of punctual literature’s superiority. The same quality of truth might be found in the diaries or correspondence of individual Londoners from the period—Waugh’s diaries, for starters, or Green’s.

In an epilogue, Heffernan makes a final bid to offer a synthesis for the unique contribution of punctual literature: each of the works under discussion, he notes, expresses “ways of resisting heroism itself.” This is not entirely surprising, since Waugh and Green are the only authors among the group who did not resist military service. Brecht fled to Denmark, then Sweden, Auden across the Atlantic (for which Waugh mocked him, under thin disguise, in Put Out More Flags ), and most of the novelists and poets who responded to questions about the war for a 1939 issue of Partisan Review (among them Henry Miller, James T. Farrell, Katherine Anne Porter, Gertrude Stein, Wallace Stevens, and Allen Tate) argued for pacifism and disengagement. Still there is nothing preventing a writer of nonfiction from mocking ideals of heroism, and several of the historians and memoirists discussed by Heffernan do just that.

Politics and Literature at the Dawn of World War II offers an appealing enticement to read some of the most inventive works of wartime literature and to recognize their contributions to the historical record. Yet it’s impossible to ignore the fact that each case study resists reduction to any universal law of punctual literature. Although novels (and plays and poems) do tend to convey “a richer quality of truth” than histories of the same events, talented memoirists, correspondents, and, yes, even historians can offer readers the same information, the same measure of contradiction and nuance, and even the same intimate engagement with historic events. They don’t, typically. (Most novelists don’t either.) But they can, and occasionally they do.

This doesn’t diminish Heffernan’s fundamental insight—that imaginative writing is especially well suited to examine a range of human experience ignored by conventional historical narratives. There may be no hard-and-fast rules of punctual literature, but there are no hard-and-fast rules of any other sort of literature either. Literature is a democracy, and not an especially law-abiding one. A writer has the freedom not to take anything seriously, even global war. A writer also has the freedom not to settle on a single perspective, moral, or conclusion. Such settling, though often the stated ambition of a work of scholarly history, is anathema to literature that takes as its subject the influence of history, politics, and philosophical thought on the lives of its characters—the so-called “novel of ideas,” which describes most of the works discussed by Heffernan. In these novels dramatic tension arises from the opposition of contradictory values, each expressed with their full strength. Without this conflict, Saul Bellow wrote, a novel of ideas “is mere self-indulgence and didacticism is simply ax-grinding. The opposites must be free to range themselves against each other and they must be passionately expressed on both sides.” Contradiction, nuance, high emotion, irrationality—in all these qualities, literature has the edge over history, though its lead is not insurmountable.

There is one dark art, however, that nonfiction cannot fully replicate: the ability of immersive narrative literature, and especially fiction, to blur, or even eradicate, the boundary between reader and subject. Readers of a history are reminded on every page, with every footnote and dutiful scholarly reference and contextual aside, of one’s distance from the action. The reader even of a memoir or a diary can never fully suspend disbelief, since the dramatic stakes of the narrative rely on its authenticity—on the assertion that the events described really happened and that the people depicted really experienced them.

Novelists don’t tend to bother about that. A novel’s success depends not on its faithfulness to reality but on the author’s ability to beguile the reader into empathizing with its hero and, for a brief time, exchanging the reality of the world for the reality of the novel.

This magic trick achieves more than an enraptured reading experience. It allows the reader to contend, on the most intimate terms, with the challenges faced by the author’s characters. In my carelessness and panic, I’ve left behind my infirm, aged father in Paris to face the Nazi invaders alone; should I abandon my children and risk my life to rescue him? I’ve injured a refugee in a road accident, but he refuses to seek medical care out of fear of extradition; do I bring him to the hospital or leave him bleeding in the road? The deeper immersion activates the reader’s own imagination. The question is no longer, Should the guerrilla fighter Robert Jordan kill on sight any stranger who obeys orders from a Fascist commander? Instead it becomes, Could I kill, if pressed into combat in a war of democracy versus tyranny? And it becomes, What would I kill for? What would I die for? What do I believe? What am I capable of? Who am I?

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