Umbrella Review

Umbrella reviews are primarily used in research fields, particularly in healthcare and social sciences, when the body of evidence on a topic has become vast and complex. It is ideal for when a researcher or decision-maker needs a comprehensive overview of a wide area, rather than just a single, focused question.

Purpose:

• To consolidate evidence: Provide a single, comprehensive summary of a broad research area where many systematic reviews and meta-analyses already exist, making the evidence more accessible for clinicians, policymakers, and decision-makers.
• To assess quality and credibility: Critically appraise the methodological quality of the included systematic reviews and meta-analyses (often using tools like AMSTAR 2) to evaluate the strength and certainty of the evidence.
• To resolve contradictions: Identify and explore reasons for conflicting or inconsistent findings across different systematic reviews on the same or related topics.
• To identify gaps: Highlight areas where evidence is lacking or insufficient to guide future research.
• To inform Guidelines/Policy: Offer the highest level of synthesized evidence to inform clinical practice guidelines and policy decisions, especially for questions involving multiple interventions or outcomes for a single condition.

Characteristics:

• Unit of Analysis: The focus is on systematic reviews and meta-analyses, not the original primary studies (like randomized controlled trials or observational studies).
• Systematic Methodology: It follows a rigorous, pre-specified methodology, including developing a protocol (often registered in databases like PROSPERO), conducting a comprehensive search, applying predefined inclusion/exclusion criteria, and extracting data.
• Broad Scope: The research question is often broader than a single systematic review, allowing for the synthesis of evidence on multiple exposures, outcomes, or interventions for a specific condition.
• Quality Appraisal: It includes a mandatory, critical assessment of the methodological quality of the included reviews.
• No New Primary Synthesis (Typically):Unlike a traditional meta-analysis, an umbrella review usually does not statistically pool data from the primary studies within the included reviews to estimate a new overall effect. Instead, it summarizes and compares the results of the already-pooled estimates from the included reviews. Some methods may involve re-analysing the meta-analytic estimates within a uniform framework (e.g., to stratify evidence credibility), but this differs from a de novo meta-analysis.
• Focus on Consistency: It aims to determine if the body of evidence is consistent, highlight potential biases, and grade the overall strength of the collective evidence.

Timescale:

The timescale for an Umbrella Review can vary significantly based on the breadth of the topic, the number of existing reviews, and the resources available (e.g., the number of reviewers).

• Generally, an Umbrella Review takes less time than a de novo systematic review or meta-analysis of primary studies, because the bulk of the work (searching, screening, and appraising primary studies) has already been done by the included reviews.
• A well-conducted Umbrella Review generally takes 4 to 12 months from protocol development to final submission, with a common duration being around 6 to 9 months.

• JBI Channel: What are Umbrella Reviews? (Assoc Prof Edoardo Aromataris): Explains the specific rationale for conducting an umbrella review, particularly when using the rigorous methodology developed by the Joanna Briggs Institute (JBI). Discusses how they differ from other systematic reviews and provides guidance on accessing the full JBI Manual for Evidence Synthesis, which contains detailed steps.
• Dr. Hassaan Tohid: HOW TO WRITE AN UMBRELLA REVIEW? Provides an 8-minute high-level overview of the review process, emphasizing the three main stages of the review (searching, analysis, and writing). Discusses the potential need for re-performing meta-analysis and calculating effect sizes if reviewing meta-analyses, and recommends external resources like the JBI review book.
• Malaysia Health Analytics: How to do Umbrella Review (Overview of Review) with Meta-IMU? (Playlist): This is a comprehensive playlist that breaks down the process into minute steps, including: Defining PICOs, defining search terms, generating PRISMA flow diagrams, assessing study overlap (redundancy), assessing risk of bias with tools like ROBIS, and interpreting confidence plots. It is useful for researchers looking for a practical, segmented walkthrough.
• Umbrella Review: Steps, Data Collection, Software Use with Example: Clearly lists the key steps (Defining question, synthesis, quality assessment, reporting). Emphasizes core features like having a comprehensive scope, guiding decisions, and identifying research gaps. Often mentions the need for critical appraisal tools like AMSTAR 2.
• The Ultimate Guide to Writing an Umbrella Review: Provides a general overview of the writing and purpose of an umbrella review, placing it at the top of the evidence hierarchy. Useful for understanding the structure and overall goals of the final paper.

Protocol

See JBI Guidance: Development of an umbrella review protocol

Reporting guideline

Reporting guidelines for specific types of overview can be found on the equator network

• Introduction to Umbrella Reviews as a Useful Evidence-Based Practice This article gives a table of the preferred reporting items for an umbrella review
• Umbrella reviews: a methodological guide, (2025)  includes a table of the different types of umbrella review with examples
• The PRIOR checklist: Reporting guideline for overviews of reviews of healthcare interventions