Literature review and systematic review: Essential information you should know
Struggling to choose between a literature review and a systematic review? Here's what you need to know:
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Purpose:
- Literature Review provides a broad overview of existing research, identifies gaps, and sets the stage for new studies.
- Systematic Review answers specific research questions using a rigorous, structured, and reproducible methodology.
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Time & Resources:
- Literature reviews are quicker and more flexible but less structured.
- Systematic reviews require more time, resources, and strict protocols but deliver highly reliable, evidence-based findings.
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Use Cases:
- Literature reviews are ideal for exploring broad topics or preparing for original research.
- Systematic reviews are best for making evidence-based decisions in fields like medicine, psychology, and policymaking.
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Methodology:
- Literature Review: Flexible search strategies, subjective selection of studies, and narrative summaries.
- Systematic Review: Exhaustive search, predefined criteria, quality assessments, and detailed documentation.
Quick Comparison
| Aspect | Literature Review | Systematic Review |
|---|---|---|
| Purpose | Broad overview, identify gaps | Answer specific questions, evidence synthesis |
| Time Investment | Weeks to months | Several months to years |
| Methodology | Flexible, narrative-based | Structured, transparent, replicable |
| Bias Risk | Higher | Lower |
| Scope | Broad, exploratory | Narrow, focused |
| Audience | General or academic | Specialized (e.g., healthcare, policymakers) |
Need help organizing your review? Tools like Sourcely simplify the process by providing access to over 200 million papers and advanced search features. Whether you're tackling a literature review or a systematic review, understanding these differences ensures you choose the right approach for your research goals.
1. Literature Review
Definition and Purpose
A literature review pulls together existing research in a specific field, analyzing and evaluating studies to summarize what’s already known. Its goal is to create a comprehensive overview of prior work, helping you build your argument or prepare for original research. As Rudestam and Newton explain:
"…your task is to build an argument, not a library."
Beyond summarizing, a literature review identifies gaps, avoids redundancy, credits prior scholars, and positions your work within the broader academic discussion. It highlights both well-established findings and areas that need further exploration.
From here, let’s look at how literature reviews are typically structured and carried out.
Methodology and Structure
Most literature reviews follow a standard structure: introduction, body, and conclusion. They can be organized in different ways depending on the research focus - chronologically, thematically, methodologically, or theoretically.
| Organizational Framework | Description | Best Used When |
|---|---|---|
| Chronological | Tracks the development of a topic over time, focusing on trends and key debates | You want to show how ideas or historical perspectives have evolved |
| Thematic | Groups content into subsections based on distinct aspects of the topic | Research reveals clear themes or recurring ideas |
| Methodological | Compares findings from various research methods | Studies use diverse approaches that need to be contrasted |
| Theoretical | Explores different theories, models, or conceptual frameworks | Competing theories or perspectives dominate the research |
Key steps for conducting a literature review include defining your research question, setting criteria for inclusion and exclusion, searching databases, reviewing results, synthesizing findings, and writing the review. Using tools like a synthesis matrix can help organize your notes and track recurring themes.
When to Use
Literature reviews are invaluable when you need to evaluate theories, assess evidence, or explore relationships between variables. They provide a consolidated understanding of research problems, highlight gaps in knowledge, support the development of new theories, and trace how a field has evolved over time.
They’re also great for uncovering unexpected connections between data and identifying areas ripe for further investigation. Before diving in, it’s helpful to conduct some initial research to ensure there’s enough material available and to refine your research question into something feasible and engaging.
Tools for Support
To streamline the process, tools like Sourcely can be a game-changer. Sourcely allows you to input entire paragraphs to quickly locate relevant studies, pulling from a database of over 200 million papers. Its advanced search features make it easier to organize sources by theme or method, helping you identify studies that align with your focus or theoretical framework.
2. Systematic Review
Definition and Purpose
A systematic review takes a more structured and methodical approach compared to a traditional literature review. The Critical Appraisal Skills Programme (CASP) defines it as:
"A systematic review is a systematic analysis of existing research on a specific topic."
The standout feature of a systematic review is its use of clear and standardized methods. Unlike literature reviews, which can be more flexible, systematic reviews follow a strict protocol designed to minimize bias and ensure reproducibility. They aim to answer specific research questions by gathering and analyzing all available evidence that meets pre-established criteria.
These reviews do more than just summarize existing research. They pinpoint gaps in knowledge, guide evidence-based decisions in research and policymaking, and highlight areas where further studies are needed. By organizing and interpreting large volumes of information, systematic reviews help determine what is effective and what isn’t.
Methodology and Structure
The methodology behind systematic reviews is what makes them distinct. Khalid S Khan and colleagues explain:
"A review earns the adjective systematic if it is based on a clearly formulated question, identifies relevant studies, appraises their quality and summarizes the evidence by use of explicit methodology."
The process typically includes several key steps to ensure thoroughness and reliability:
- Framing the research question: Frameworks like PICO (Population, Intervention, Comparison, Outcome) are commonly used to define the scope.
- Developing a protocol: Establishing a protocol early on provides structure, reduces bias, and allows for registration in databases like PROSPERO.
- Comprehensive search strategies: Searching across multiple resources is essential. Collaborating with librarians can enhance the quality of search strategies.
- Study selection and data extraction: Conducted by multiple reviewers, this step reduces selection bias and ensures consistency.
- Risk of bias assessment: Evaluating the quality of included studies is crucial.
- Synthesis of results: Findings are synthesized either qualitatively or quantitatively, depending on the data.
Transparency and reproducibility are central to the credibility of a systematic review, setting it apart from traditional literature reviews.
When to Use
Systematic reviews are most effective when there’s a need for strong evidence to answer specific clinical or research questions. They are particularly useful in fields like medicine, psychology, and policymaking, where decisions can have significant consequences. This approach is ideal when minimizing bias and ensuring reproducibility are critical, such as in the analysis of clinical trials, medical research, or large social science datasets. While systematic reviews demand considerable time, expertise, and resources compared to literature reviews, they provide authoritative and reliable findings, making them invaluable for high-stakes decision-making.
Tools for Support
To support the detailed process of a systematic review, tools like Sourcely can be incredibly helpful. Sourcely simplifies the initial phase of identifying relevant studies. By entering specific search terms or text excerpts related to your research question, you can quickly generate a list of potential studies. Its advanced filtering options - such as narrowing results by publication date, study type, or subject area - align with the systematic approach. While manual screening and quality assessment remain essential, Sourcely ensures you start with a comprehensive and relevant pool of studies, reducing the chance of missing critical research.
Differences Between Literature Review and Systematic Review
How Methods and Structure Differ
Building on earlier definitions and methodologies, this section delves into how specific review methods and structures vary. These differences are critical in distinguishing literature reviews from systematic reviews.
Search Strategy Approaches
The search strategies for each review type highlight key differences in their methodological approaches. Systematic reviews demand an exhaustive search process designed to capture every relevant study possible. This involves searching across multiple databases, including less conventional sources like government reports and conference proceedings, while tailoring search syntax for each platform.
In contrast, literature reviews offer more flexibility. Authors rely on their professional judgment and are not required to document every decision extensively.
Systematic reviews also emphasize transparency, requiring detailed records of search decisions, such as database selections, keywords, and Boolean operators . Literature reviews, however, allow authors to adapt their search approaches without the same level of documentation.
Eligibility Criteria and Study Selection
Systematic reviews operate with predefined eligibility criteria that guide which studies to include. These criteria often cover aspects like publication dates, study designs, participant demographics, and outcome measures.
On the other hand, literature reviews adopt a more subjective approach. Studies are selected based on their relevance to the topic and the author’s expertise, often without predefined criteria. While this flexibility allows for broader exploration, it also introduces the risk of bias.
Additionally, systematic reviews frequently involve a dual independent review process, where multiple researchers independently assess each study against the set criteria. This method enhances consistency and reduces individual bias.
Structural Organization and Format
The structure of each review type reflects its methodology. Here's a comparison:
| Aspect | Systematic Review | Literature Review |
|---|---|---|
| Overall Structure | Highly organized with mandatory sections: introduction, methods, results, discussion | Flexible, often arranged by themes, trends, or chronology |
| Methods Section | Detailed documentation of search strategies, databases, and quality assessment | Brief or absent description of methods |
| Search Documentation | Complete records of search strings, database names, and rationales | General overview of sources consulted |
| Study Selection | Flowchart detailing the screening process | Simple listing of included studies |
| Quality Assessment | Formal evaluation using standardized tools | Informal or no quality evaluation |
| Results Presentation | Systematic synthesis, often with statistical analysis | Narrative summary grouped by topic or theme |
Assessment and Quality Control
Systematic reviews incorporate standardized tools to assess the quality of included studies and the strength of their evidence. Literature reviews, by contrast, may include comments on study quality, but these are typically informal and based on the author’s judgment rather than standardized criteria.
Practical Implementation Differences
The practical execution of these reviews also sets them apart. Systematic reviews involve meticulous planning: defining key concepts, testing search strings, and refining them through pilot searches. Synonyms and alternative terms are identified for each concept, and search strategies are adapted for different databases .
Literature reviews, however, are more iterative. Authors can adjust their search terms as they uncover new ideas, without needing to document or justify every change. This flexibility often makes literature reviews quicker to complete, although it may sacrifice thoroughness.
Time investment is another major distinction. Literature reviews, once scoped, can be completed relatively quickly. Systematic reviews, however, require substantial upfront effort, including protocol development and detailed documentation before the actual search begins. Reflecting this trend, the term "systematic reviews" has become more commonly used in publications than "literature reviews" in recent years.
Recognizing these differences helps researchers choose the review type that aligns with their goals and resources - whether they need the comprehensive, bias-reducing approach of a systematic review or the broader, more adaptable scope of a literature review.
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Choosing the Right Review Type
When deciding between a literature review and a systematic review, it’s essential to weigh your research goals and the resources at your disposal. Each approach serves distinct purposes, and the right choice depends on what you aim to achieve and the constraints you face.
Research Question Specificity
A systematic review is ideal when your research centers on a specific, well-defined question that demands clear, evidence-based answers. For instance, systematic reviews are often used to evaluate clinical or research questions, such as the effectiveness of treatments or interventions.
On the other hand, literature reviews are better suited for broader, more exploratory questions. If you're trying to map out a field or identify general trends, this approach works well. For example, a literature review would fit a question like, "What factors influence student motivation?" But if your question is more focused, such as "Does cognitive behavioral therapy reduce anxiety symptoms in adolescents compared to medication?" then a systematic review would be the better choice.
Time and Resource Constraints
The time and resources you have available can heavily influence your decision. Literature reviews are typically quicker to complete, often taking weeks to a few months. Systematic reviews, however, are far more time-intensive, requiring several months or even years to finish due to their rigorous methodology.
Resource availability is another key consideration. Systematic reviews often require a team of researchers to independently assess studies and minimize bias through a dual-review process. In contrast, literature reviews can be managed by a single researcher with the right expertise, making them more feasible for smaller projects.
Intended Audience and Purpose
The audience and purpose of your research also play a role in determining the best approach. Literature reviews are effective for general audiences or when providing background information for new research projects. They help set the stage by offering a broad overview of a topic.
Systematic reviews, however, cater to specialized audiences, such as healthcare professionals, policymakers, or researchers. These groups rely on the thorough, evidence-based findings of systematic reviews for making critical decisions, such as developing treatment guidelines or creating policies.
Practical Decision Framework
Here’s a quick way to decide:
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Opt for a literature review if you’re:
- Exploring broad themes or emerging topics
- Facing tight deadlines
- Conducting preliminary research to identify gaps
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Opt for a systematic review if you’re:
- Addressing specific questions about treatment or intervention effectiveness
- Equipped with substantial time and resources
- Aiming to inform clinical practice or policy decisions
Hybrid Approaches for Limited Resources
If you’re working under time or resource constraints but still want some level of rigor, hybrid approaches like rapid and scoping reviews can be a solution. Rapid reviews use systematic methods but streamline the process to meet tight deadlines, though they may sacrifice some depth. Scoping reviews, meanwhile, offer more structure than traditional literature reviews while remaining more flexible than systematic reviews.
Making the Final Decision
Ultimately, literature reviews are excellent for gaining broad, quick insights, while systematic reviews provide detailed, targeted evidence. Both approaches have their place in advancing research. Tools like Sourcely can support either method, helping you efficiently find relevant studies no matter which path you choose.
Improving Review Quality with Sourcely
For researchers, finding reliable sources quickly is a must, especially when working on literature or systematic reviews. Sourcely simplifies this process with its AI-powered tools, designed to help U.S.-based researchers access credible academic literature. Whether you're tackling a broad literature review or a detailed systematic review, Sourcely ensures your work is both efficient and trustworthy.
AI-Powered Text-to-Source Matching
With Sourcely, you can paste entire paragraphs of text, and the platform will instantly identify relevant academic sources. It even highlights the parts of your text that need citations and provides matching references. This feature not only saves time but also helps maintain academic integrity throughout your review process.
Advanced Filtering for Precise Results
Sourcely's filtering tools allow you to fine-tune search results by publication year, author, relevance, and specific keywords. This is especially helpful for systematic reviews that require strict inclusion criteria. As the Science Grad School Coach notes:
"What sets Sourcely apart is its advanced filtering system. Not only can you filter by publications and citations, but you can also include or exclude specific keywords to refine your search. With Sourcely, finding the perfect citation for any sentence in your paper becomes a quick and painless process."
For broader literature reviews, these filters help narrow down results from Sourcely's extensive database of over 200 million papers [9, 41].
Simplified Citation Management
Sourcely takes the hassle out of managing citations. The platform summarizes sources and exports citations in multiple formats, which is especially valuable for systematic reviews where accurate documentation is critical. Many sources also include free PDF downloads, giving you easy access to full-text articles.
Real-World Impact
Sourcely has already made a mark with more than 100,000 users. Researchers consistently report that it improves their workflow and makes sourcing literature significantly more efficient.
Flexible Pricing for Researchers
Sourcely offers several pricing options to meet different research needs:
| Plan | Price | Best For |
|---|---|---|
| SourcelyFREE | $0/month | Testing the platform (300-character limit) |
| Try Once | $7 (one-time) | Small projects or one-time use |
| Pro Monthly | $17/month | Ongoing research projects |
| Pro Yearly | $167/year | Regular researchers (saves $37 annually) |
| Believer | $347 (one-time) | Long-term researchers (3-year access) |
Graduate students and early-career researchers working on extensive literature reviews may find the Pro Monthly plan ideal. Meanwhile, those conducting multiple systematic reviews might benefit from the Pro Yearly plan. For frequent users, the Believer plan offers excellent long-term value.
How to Use Sourcely
Getting started with Sourcely is easy. Paste your essay or a paragraph into the platform, and let it find the sources for you. For more specific results, use the "Filters" feature to apply criteria that align with your review's requirements. This intuitive process speeds up your research while ensuring high-quality results.
Advantages and Disadvantages
Understanding the strengths and limitations of each review type can help you make informed decisions, shaping how much time, effort, and credibility your research garners.
| Aspect | Literature Review | Systematic Review |
|---|---|---|
| Time Investment | Quicker but less structured (hours to six months) | Slower but more thorough (9–18 months) |
| Methodology | Flexible and narrative-based | Structured with clear, transparent protocols |
| Scope Coverage | Covers a wide range of topics and sources | Focused and exhaustive within preselected databases |
| Bias Risk | Higher chance of subjective bias | Lower bias due to stringent, replicable methods |
| Research Question | Offers a broad overview of knowledge areas | Focuses on answering specific, evidence-based questions |
| Quality Control | Relies on the author's judgment for source selection | Follows strict inclusion/exclusion criteria and quality checks |
These differences highlight when each method is best suited to meet your research objectives.
When Literature Reviews Work Best
Literature reviews shine when you need to provide background information rather than draw definitive conclusions. They are particularly useful in dissertation introductions, journal article background sections, and grant proposals. If you're working in a developing field where evidence is sparse, or you need to analyze trends and theoretical frameworks, literature reviews allow you to synthesize diverse perspectives without being tied to rigid methodologies.
When Systematic Reviews Are Essential
Systematic reviews are invaluable in scenarios requiring precise, evidence-driven analysis, such as healthcare decision-making. They are ideal for standalone journal articles, Cochrane reviews, or meta-analyses for PhD theses, where identifying and rigorously evaluating every relevant study is crucial.
Hidden Challenges to Consider
Even with their rigor, systematic reviews are not without challenges. Issues like flawed search strategies and research redundancy can undermine their credibility. A BMJ survey revealed that of 73 randomly selected meta-analyses published in 2010, two-thirds had at least one additional meta-analysis on the same topic by early 2013, highlighting the problem of redundancy.
"Considering the pivotal role that systematic reviews have in medical decision-making due to having apparently transparent, objective, and replicable processes, a failure to appreciate and regulate problems with these highly cited research designs is a threat to credible science."
– Lesley Uttley et al.
Tools like Sourcely can help mitigate these issues by streamlining the search process and ensuring more comprehensive coverage.
Practical Implications for Your Research
Striking the right balance between these approaches is essential. Literature reviews prioritize speed and adaptability but may lack depth and objectivity. On the other hand, systematic reviews deliver reliable, replicable findings but require significant time and expertise.
Think about your audience's expectations. Academic committees and journal reviewers often prefer systematic approaches for specific research questions, while exploratory or theoretical work may benefit from the flexibility of literature reviews. The key is to align your review type with your research goals, available resources, and the level of evidence required to ensure your work is both effective and impactful.
Conclusion
Literature reviews and systematic reviews each play a vital role in academic research, but choosing the right one depends on understanding their distinct purposes and methods. Literature reviews are ideal for offering broad overviews of a topic, making them useful in contexts like dissertation introductions, grant proposals, or early-stage research where mapping the research landscape is key.
On the other hand, systematic reviews are designed to provide detailed, evidence-based answers through standardized and reproducible methods. They are particularly valuable in fields like healthcare, where precise and comprehensive evidence is often required for decision-making and meta-analyses. While systematic reviews demand more time and resources compared to literature reviews, they deliver the level of reliability and rigor that specialized audiences and critical decisions often require.
The choice between these approaches hinges on a few factors: the scope of your research question, the time and resources you can dedicate, and the needs of your audience. Broad, exploratory questions align well with the flexibility of literature reviews, while specific, evidence-driven questions are better suited to the structured approach of systematic reviews.
Incorporating tools like Sourcely can further enhance the review process. These digital solutions streamline workflows, making both quick literature reviews and in-depth systematic reviews more efficient and accurate. By selecting the appropriate review type and leveraging smart tools, you can boost the quality, credibility, and impact of your research.
FAQs
What are the key methodological differences between a literature review and a systematic review?
The main distinction between the two lies in their structure and methodology. A literature review takes a more open-ended, narrative approach. It provides an overview of existing knowledge on a topic, often serving as a way to set the stage or offer background for further research. It doesn't adhere to rigid procedures, allowing for a broader and more descriptive exploration.
On the other hand, a systematic review is far more structured and methodical. It follows a clearly defined protocol with strict criteria for selecting and analyzing studies. The goal is to deliver a thorough and impartial synthesis of evidence to address specific research questions. This structured approach ensures clarity and reproducibility, making systematic reviews a key element in evidence-based research.
How do I decide if a literature review or a systematic review is best for my research project?
Choosing between a literature review and a systematic review depends on what you aim to achieve and how detailed your research needs to be.
A literature review is a great option if your focus is broad or exploratory. It provides a summary of existing research, helping to set the stage for your study or highlight areas that need more attention. This approach is more flexible and less formal, making it perfect for getting a general understanding of a topic or when you’re just starting to dive into a subject.
In contrast, a systematic review is designed for tackling specific, well-defined research questions. This method involves a strict, structured process to collect and analyze evidence, ensuring the findings are thorough and reliable. It’s especially common in fields like healthcare and social sciences, where precise evidence and detailed analysis are essential.
To decide, think about how complex your research question is and whether you need a wide-ranging overview or a detailed, structured approach to answer it.
What tools can help simplify the process of conducting a literature or systematic review?
When it comes to conducting a literature review or a systematic review, the right tools can make your process smoother and more precise. Specialized software can help you stay organized, manage your sources, select relevant studies, extract key data, and even pull everything together into a cohesive synthesis.
Popular tools for systematic reviews are specifically designed to handle these complex tasks, helping researchers save time without compromising on detail or accuracy. Using these resources can streamline your workflow and enhance the overall quality of your research.
