This is a question that I’m often asked, or I have a request to help someone with a systematic review, only to find that what they really need help with is a systematic search of the literature for a literature review. So what is the difference?
To help address this question I’ll start by looking at some definitions.
The Cochrane Library gives a helpful definition on its website:
“A systematic review attempts to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a specific research question. Researchers conducting systematic reviews use explicit, systematic methods that are selected with a view aimed at minimizing bias, to produce more reliable findings to inform decision making.”
A literature review is a comprehensive summary of previous research on a topic. The literature review surveys scholarly articles, books, and other sources relevant to a particular area of research. The Royal Literary Fund gives some useful information about what a literature review is and the main objectives of a literature review.
Both provide summaries of the literature published on a topic, but they vary significantly in terms of goals, components, methodologies, and the approach to evidence-based practice.
In essence a systematic review will focus on a question and will look at all of the evidence that is available to address that question and appraise the studies to see if they are reliable or not. The main purpose of the systematic review is to eliminate bias, and rigorous methods are used to gather, analyse, interpret and summarize the evidence. It is known as a systematic review because the approach to searching the literature is done is a systematic way, using strict protocols, and systematic methods are used to evaluate all of the evidence. In comparison, a literature review will provide a summary of the literature on a topic and does not necessarily focus on a single question. Clearly defined methodologies for searching the literature and analysing the evidence may not be used. The review is a comprehensive study and interpretation of the literature in order to address a topic, and the approach to searching the literature will be done in a systematic way, but the strict protocols, comprehensive search strategies and inclusion and exclusion criteria, required of a systematic review, are not necessary for a literature review.
To highlight the differences between the two approaches, Bettany-Saltikov (2010) has produced a table comparing the two approaches (see Bettany-Saltikov, J. (2010). Learning how to undertake a systematic review: Part 1. Nursing Standard, 24 (40): 47-55. doi: 10.7748/ns2010.08.24.50.47.c7939).
More help and advice
More help and advice about systematic literature searching (not a systematic review) is available via a CANVAS course. The Research Skills Team can offer help with searching databases and techniques needed to put together a good search strategy, but cannot do systematic searches for researchers. If you need more help with doing a systematic review, have a look at the Cochrane Interactive Learning Resource; this interactive resource is an online introductory training course on how to conduct a systematic review of interventions.
Have you carried out a literature review? Was it systematic? If so, what tips and resources do you recommend to others?