Cochrane Library

The Cochrane Library is a collection of databases containing high quality, independent evidence to inform healthcare decision making. Its cornerstone is the Cochrane Database of Systematic Reviews (CDSR), which publishes Cochrane Reviews and their protocols, prepared by author teams to Cochrane's methodological standards. The Library also includes the Cochrane Central Register of Controlled Trials (CENTRAL), a database of reports of randomized and quasi randomized controlled trials, and Cochrane Clinical Answers, short clinically focused summaries drawn from Cochrane Reviews.

The Cochrane Library is widely regarded as the single most important source of systematic review evidence for healthcare. Clinical guideline developers, health technology assessment agencies, policy makers, clinicians, and researchers worldwide rely on Cochrane Reviews for the best available evidence on the effectiveness and safety of health interventions. Cochrane Reviews can be updated when new evidence emerges, and a small number are maintained as living systematic reviews, but each review is only as current as its last search. CENTRAL is one of the most comprehensive sources of clinical trial records and is a recommended database for systematic review searching. The Cochrane Collaboration's commitment to independence, methodological rigor, and transparency sets the standard for evidence synthesis.

The reviews in the Library are written by author teams from a global network of researchers, many of whom contribute their time free of charge. Since Cochrane's restructuring from 2023, these teams work with Cochrane Review Groups (each specializing in an area of health, such as breast cancer or hypertension), Thematic Groups or Evidence Synthesis Units, while a Central Editorial Service manages the editorial and peer review process. Authors of intervention reviews follow the methods described in the Cochrane Handbook for Systematic Reviews of Interventions, which provides detailed guidance on question formulation, search strategy development, study selection, data extraction, risk of bias assessment, meta analysis, and interpretation. Other review types, such as diagnostic test accuracy reviews, follow their own Cochrane guidance.

The Cochrane Database of Systematic Reviews (CDSR) publishes both full reviews and protocols (which describe the planned methods for reviews in progress). Reviews undergo editorial and peer review before publication and may be updated when new evidence or methods are likely to change their findings. The CDSR is indexed in major bibliographic databases including PubMed/MEDLINE.

CENTRAL (the Cochrane Central Register of Controlled Trials) compiles records of controlled trials from MEDLINE, Embase, and other sources, supplemented by hand searching of journals and conference proceedings by Cochrane contributors. It is one of the most comprehensive sources of trial records for systematic review searches.

The Library also includes Cochrane Clinical Answers, short clinically focused summaries of Cochrane Review evidence for point of care decisions. Databases it once hosted, including the Database of Abstracts of Reviews of Effects (DARE), the Health Technology Assessment database, the NHS Economic Evaluation Database and the Cochrane Methodology Register, are no longer part of it. Access varies: abstracts and plain language summaries are free to read, Cochrane Reviews become free to read 12 months after publication, and protocols and editorials have been published open access since 2025. National provisions in some countries give everyone there free access, Cochrane offers free access in many low and middle income countries, and elsewhere full immediate access is by subscription.

The Cochrane Library should be searched as a primary resource whenever conducting a systematic review of health interventions. CDSR should be checked to identify existing Cochrane Reviews on the topic of interest before undertaking a new review. CENTRAL should be included in the search strategy for identifying relevant trials. Clinicians and guideline developers should consult Cochrane Reviews for synthesized evidence on treatment effectiveness and safety, checking each review's search date and update status. Researchers should consider contributing to Cochrane Review Groups to participate in the production and updating of high quality evidence syntheses.

A common error is treating Cochrane Reviews as the final word on a topic without checking whether a more recent review with additional studies has been published by other groups. Cochrane decides whether to update each review according to need, so there can be long gaps between updates during which significant new evidence accumulates. Another mistake is confusing the Cochrane Library with Cochrane itself; the Library is the publication platform, while Cochrane is the organization that produces the reviews.

Researchers sometimes also fail to search CENTRAL when conducting systematic reviews, missing trial records that are not available in MEDLINE or Embase alone. Finally, some researchers cite "the Cochrane Review" without specifying which review or what version, which is problematic because Cochrane Reviews are updated and different versions may contain different evidence and conclusions.

In a hypothetical example, a clinical guideline committee developing recommendations for the management of gestational diabetes searches the Cochrane Library and identifies three relevant Cochrane Reviews: one on dietary interventions (including 19 trials), one on pharmacological treatments (including 46 trials), and one on glucose monitoring strategies (including 12 trials). The committee uses the evidence from these reviews, along with updated searches for trials published since the most recent review update, to formulate their recommendations. They note that the Cochrane Reviews provide risk of bias assessments and GRADE ratings that facilitate the guideline development process.