Evidence Synthesis in the Sciences and Social Sciences

What to Consider

• Scope: Is the question narrow or broad?
• Time Constraints: Systematic reviews may take 12–18 months; rapid reviews are faster but less rigorous.
• Nature of the Evidence: Does your field have quantitative, qualitative, or mixed-methods research?

Helpful Tools

• Right Review: Assists researchers in selecting the most appropriate knowledge synthesis method for their research questions. Freely available online, this tool offers guidance on various quantitative and qualitative review methods through a series of straightforward questions, helping users determine the best approach for their specific needs.
• Systematic Review Decision Tree: This flowchart, titled What Type of Review is Right for You? is provided courtesy of the Cornell University Library.

Some Types of Reviews

Type of Review	Definition	Example Question
Systematic Review	Comprehensive, structured synthesis of studies to answer a specific research question. May include a meta-analysis.	Does mindfulness reduce anxiety in college students compared to no intervention?
Meta-Analysis	Statistical synthesis of quantitative data from multiple studies.	What is the effect size of exercise on reducing symptoms of depression?
Scoping Review	Broad mapping of existing evidence to explore knowledge gaps. Does not synthesize results like a systematic review.	What interventions are used to manage stress among university students?
Narrative Review	Qualitatively summarizes existing research on a topic, offering an overview of trends, theories, and gaps without strict systematic methods or a focused research question.	What are the historical and cultural perspectives on the relationship between mindfulness and mental health?

For a comprehensive typology of reviews*, see:

Sutton, A., Clowes, M., Preston, L., & Booth, A. (2019). Meeting the review family: Exploring review types and associated information retrieval requirements. Health Information and Libraries Journal, 36(3), 202–222. https://doi.org/10.1111/hir.12276

*The article focuses on health sciences reviews, but the typology is applicable across several disciplines.

Consider a Narrative Review After consulting the above resources, you may determine that you intend to conduct a narrative review, rather than a more specialized synthesis of the evidence. If that is the case, you may find the following publications on narrative reviews helpful: Literature Review: A Research Journey (a tutorial, courtesy of Harvard's Gutman Library, on conducting narrative literature reviews) Baumeister, R. F., & Leary, M. R. (1997). Writing Narrative Literature Reviews. Review of General Psychology, 1(3), 311–320. https://doi.org/10.1037/1089-2680.1.3.311 (an article that walks readers through the process of producing a high quality narrative review) Greenhalgh, T., Thorne, S., & Malterud, K. (2018). Time to challenge the spurious hierarchy of systematic over narrative reviews? European Journal of Clinical Investigation, 48(6), e12931-n/a. https://doi.org/10.1111/eci.12931 (an article that describes the form and facility of high quality narrative reviews as complementary to systematic reviews) Baumeister, R. F., & Leary, M. R. (1995). The Need to Belong: Desire for Interpersonal Attachments as a Fundamental Human Motivation. Psychological Bulletin, 117(3), 497–529. https://doi.org/10.1037/0033-2909.117.3.497 (an example of a well-crafted narrative review)

Why This Matters: A clearly defined research question ensures focus and guides every step of the synthesis process.

Use a Framework to Structure Your Question:

• PICO: Population, Intervention, Comparison, Outcome
• PICo: Population, Phenomenon of Interest, Context (for qualitative research)
• SPICE: Setting, Perspective, Intervention, Comparison, Evaluation
• SPIDER: Sample, Phenomenon of Interest, Design, Evaluation, Research Type

Example Using PICO:

• Population (P): College students.
• Intervention (I): Mindfulness-based stress reduction.
• Comparison (C): Cognitive behavioral therapy.
• Outcome (O): Reduction in anxiety symptoms.
• Final Question: Is mindfulness more effective than CBT for reducing anxiety in college students?

Before embarking on your review, look for extant or in-process reviews on your topic. This ensures that you won't be rebuilding the wheel. The following are databases wherein you may search for registered protocols:​

• ​Prospero​
• Campbell Systematic Reviews​ (In the Advanced Search, try looking up "protocol" in the Abstract field.)
• Cochrane Reviews​ (See the Protocols tab.)
• OSF​ (Click on Search in the top navigation bar, and then click on the Registrations tab.)
• Protocols.io​
• Joanna Briggs Institute​ (JBI registers protocols and specifies the components that comprise a JBI protocol in its reviewer's manual.)

Additionally, you may search for recently published reviews on your topic. Here are some places to look:

• ​Various institutional repositories
• Various pre-print servers
• Various subject-specialized library databases
• Annual Reviews database

Definition: Criteria used to decide which studies to include or exclude.

How to Define Criteria:

1. Population: Who is being studied? Age, gender, location, etc.
2. Intervention/Exposure: What is being done or experienced?
3. Comparison: What alternative interventions, if any, are considered?
4. Outcome: What outcomes are measured?

Example:

• Inclusion: Studies examining adults (18–65) with anxiety disorders; randomized controlled trials; interventions lasting > 6 weeks
• Exclusion: Studies with children; non-English language studies.

Team Roles:

• Lead Reviewer: Methodology oversight, quality control, and integration of findings.
• Librarian: Search strategy development (see service levels available).
• Subject Experts: Study inclusion, data extraction, and analysis.
• Project Manager: Keeps timelines and milestones on track.
• Data Analyst: Statistical synthesis or qualitative analysis.

Best Practice: A minimum of two reviewers for screening and a third reviewer to resolve conflicts.