Skip to Main Content

Systematic Reviews

This guide explains the principles of systematic reviews and offers advice on getting started with your systematic literature search.

Systematic Reviews at UCLA Library

The Biomedical Library’s Systematic Review Service is being reconfigured and improved. The service will be restored on December 1, 2023. Systematic Reviews currently scheduled will proceed as arranged without interruption. 

What Is a Systematic Review?

A systematic review is fundamentally different from a traditional narrative review. For more information, see Types of Literature Reviews.

A systematic review is defined as: "A scientific investigation that focuses on a specific question and that uses explicit, planned scientific methods to identify, select, assess, and summarize the findings of similar but separate studies. It may or may not include a quantitative synthesis of the results from separate studies (meta-analysis) depending on the available data." IOM p 1.

According to the Cochrane Handbook, section 1.2.2, "the key characteristics of a systematic review are:

  • a clearly stated set of objectives with pre-defined eligibility criteria for studies;
  • an explicit, reproducible methodology;
  • a systematic search that attempts to identify all studies that would meet the eligibility criteria;
  • an assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias; and
  • a systematic presentation, and synthesis, of the characteristics and findings of the included studies."

Green S, Higgins JPT, Alderson P, Clarke M, Mulrow CD, Oxman AD. Chapter 1: Introduction. In: Higgins JPT, Green S (editors), Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 (updated March 2011). The Cochrane Collaboration, 2011. Available from

Is Your Review Systematic?

Are you sure your review is systematic? A systematic review requires…

You can also use this primer geared towards beginners for a better understanding of the differences between types of reviews and the overall steps of a systematic review:

  • Craig A. Umscheid; A Primer on Performing Systematic Reviews and Meta-analyses, Clinical Infectious Diseases, Volume 57, Issue 5, 1 September 2013, Pages 725–734,

Why Do a Systematic Review?

The goal of a systematic review is to reduce bias and produce high quality evidence.

Rigorous systematic reviews are at the top of representations of research evidence (see below). The synthesis of multiple high-quality studies creates a single product out of all the best known evidence.