Overview of reviews, umbrella review, review of reviews: what the different names mean, whether they differ, and how to report a review of reviews correctly.
Search the literature for reviews that synthesize other reviews and you will find at least four names for what is largely the same thing: overview of reviews, umbrella review, review of reviews, and meta-review. Authors use them interchangeably, journals accept all of them, and newcomers reasonably wonder whether they are missing a distinction.
Mostly, they are not. The terms overlap heavily. But the naming does carry some signal, and how you report one of these reviews has genuine requirements that are easy to get wrong. This piece is about the terminology and the reporting. For how to actually conduct one, including the critical problem of overlapping primary studies, see our separate guide on umbrella reviews.
Overview of reviews, umbrella review, review of reviews, and meta-review all refer to a review whose included studies are systematic reviews rather than primary studies. In practice the terms are used interchangeably and no firm, universally accepted distinction separates them.
If there is a tendency, it is that "overview of reviews" is the term favoured in Cochrane and more formal methodological contexts, while "umbrella review" is the more common general usage, particularly outside Cochrane. Choose one term, define what you mean by it in your methods, and use it consistently.
This is the question people want a clean answer to, and the honest answer is that the literature does not provide one.
Some authors have attempted to draw distinctions, for instance suggesting that an overview focuses on comparing interventions across reviews while an umbrella review summarizes evidence across many outcomes or conditions. These distinctions are not consistently observed in practice. You will find published reviews using each label to do each job.
The practical consequence: do not assume a reader knows what you mean from the label alone. Whichever term you choose, state explicitly in your methods what your review does, that its unit of analysis is systematic reviews, what kinds of reviews it includes, and what it aims to produce. The definition in your methods section carries the meaning. The label is just a title.
| Term | Common usage | Notes |
|---|---|---|
| Overview of reviews | Cochrane and formal methodological contexts | Often the preferred technical term |
| Umbrella review | Widespread general usage | The most commonly encountered label |
| Review of reviews | Plain-language description | Descriptive and unambiguous |
| Meta-review | Occasional usage | Less common; can be confused with meta-analysis |
Reporting a review of reviews has requirements beyond those of an ordinary systematic review, and this is where these reviews most often fall short.
Define your unit of analysis clearly. State that your included studies are systematic reviews, and define what you counted as a systematic review. Review quality varies enormously, and a reader needs to know whether you included anything self-labelled as a review or applied a definition.
Report the overlap between reviews. This is the single most important reporting item and the one most often omitted. Included reviews frequently share primary studies, so the same trial can be counted multiple times across your reviews. If you do not report the degree of overlap, a reader cannot tell whether two reviews agreeing represents two independent lines of evidence or one study counted twice. Report which primary studies appear in which reviews, and quantify the overlap where you can.
Report the appraisal of your included reviews. You are appraising reviews, not primary studies, so the tools differ. State which you used, commonly AMSTAR 2 for methodological quality or ROBIS for risk of bias, and report the results for each included review. A conclusion drawn from low-quality reviews deserves less confidence, and readers need to see that.
Report the search for reviews. Your search targeted reviews, not primary studies, which usually means review-specific filters and databases that index reviews. Document it fully, as in any systematic review.
Report a flow diagram. Account for every record from the initial search down to the final included reviews, as PRISMA requires.
Be explicit about the currency of the underlying evidence. Your included reviews each ran their searches at different times, some possibly years ago. The evidence base you are summarizing is therefore older than your own search date, sometimes considerably. Say so, because a reader who assumes your review reflects the current literature will be misled.
There is no single dedicated reporting standard that has achieved the universality PRISMA has for systematic reviews. In practice, report against PRISMA, adapting the items to the review level, and supplement it with the additional items above, particularly overlap, review appraisal, and the currency of the underlying evidence.
Cochrane provides methodological guidance for overviews of reviews within its handbook, and JBI provides guidance for umbrella reviews. Following one of these explicitly, and saying which you followed, is the clearest route. It tells reviewers you applied an established method rather than improvising.
Not reporting overlap. The defining failure. Without it, apparent agreement between reviews cannot be interpreted.
Appraising with the wrong tools. Using RoB 2 or similar primary-study tools on systematic reviews is a category error. Use AMSTAR 2 or ROBIS.
Vague inclusion criteria for reviews. "Systematic reviews on the topic" is not specific enough, because the quality of things calling themselves systematic reviews varies wildly. Define what qualified.
Ignoring the age of the underlying evidence. Presenting the review as current when its included reviews searched years ago overstates its currency.
Using the terms as if they were technical. Writing "this is an umbrella review, not an overview" as though the distinction is established will confuse rather than clarify. Define what you did.
What is an overview of reviews? A review whose included studies are systematic reviews rather than primary studies. It synthesizes what the existing reviews on a topic collectively show.
Is an overview of reviews the same as an umbrella review? In practice, yes. The terms are used interchangeably and no firm, universally accepted distinction separates them. "Overview of reviews" tends to appear in Cochrane and formal methodological contexts; "umbrella review" is more common generally.
What should I call my review? Pick one term, define clearly in your methods what your review does, and use the term consistently. The definition carries the meaning, not the label.
What is the most important thing to report? The overlap between your included reviews. Without it, readers cannot tell whether agreement between reviews reflects independent evidence or the same primary studies counted repeatedly.
Which reporting standard should I follow? Report against PRISMA adapted to the review level, and follow established methodological guidance from Cochrane or JBI, stating which you used.
Overview of reviews, umbrella review, review of reviews, and meta-review largely name the same thing, and no reliable distinction separates them in practice. Choose a term, define your method explicitly, and stop worrying about the label.
Spend the effort on the reporting instead, where the real requirements sit: define your unit of analysis, report the overlap between included reviews, appraise those reviews with tools built for reviews, and be honest about how old the underlying evidence is. Those four items are what let a reader trust a synthesis built on other people's syntheses.
Synthesizing across reviews? Verflux supports the search, screening, and appraisal underneath any evidence synthesis.
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