What is a Systematic Review?
Systematic reviews are more commonly associated with medicine and evidence based research to inform clinical decisions and treatments. However, critical reviews or the systematic synthesis of research findings were already being published in disciplines such as the social sciences in the early 1970s in order to provide evidence to inform service and policy decisions. 
It was in 1972 that Archie Cochrane, a British epidemiologist, wrote about the need for more clinicians and medical practitioners to use randomised controlled trial findings to inform them about the best drug treatments and therapies for patients. 
In 1979, he went on to write that there was a significant lack of critical summaries of research evidence in the medical profession. Cochrane argued it was essential for clinicians to start periodically critically reviewing a range of randomised controlled trials to really ensure best practice in health care decisions.  This is how critical reviews evolved in medicine into the systematic reviews that are published today.
|Systematic Review Guide|
A systematic review implements a standardised approach to gathering evidence relating to a specific research question. The evidence is taken from a systematic search of an exhaustive set of studies, and the data analysed in context to assess the strength of the findings. The quality of systematic reviews varies, although published Cochrane Reviews use rigorous scientific methods and are sometimes considered to be the ‘gold standard’. A systematic review does not necessarily have to adhere to all the Cochrane requirements if it is going to be published elsewhere. There are organisations other than Cochrane that have developed standards for systematic reviews. Consult the new systematic review library guide for more detailed information.
Systematic reviews have some unique features that make them differ from standard literature reviews. Below are some requirements of published Cochrane systematic reviews.
- Should have more than one author. This is effective in reducing potential author bias in selection of studies and data extraction, and to help detect any errors.
- Can be replicated (and therefore verified) due to the comprehensive documentation of the search and selection methodologies used.
- Poor quality studies are eliminated (via pre-defined exclusion criteria) even when there are few other studies available. This can provide clarity in areas previously thought to show opposing conclusions.
- Where possible, an international perspective is taken and results considered in a broad context.
- Must be updated every two years or include an explanation as to why this hasn’t happened.
Some systematic reviews will include a meta-analysis when assessing the effectiveness of a healthcare outcome. A meta-analysis is a statistical technique that combines the findings of relevant studies and analyses the resulting data set. For more information see the Cochrane Handbook.
Rise of systematic reviews
There has been a proliferation of systematic reviews being published and the number continues to rise. According to a recent study, over a 10 year period from 2004 to 2014 the number of indexed systematic reviews in Medline database went from 2,500 to 8,000. The authors of the study suggest that the reasons for this may vary, including funder requirements for systematic reviews for research proposals and also the increase and availability of journals accepting systematic reviews. 
In order to ensure the quality of a systematic review, it is important to seek professional advice, particularly in the selection of appropriate library resources to search and methods of searching. The new library guide has been developed to address the needs of both students and researchers, and can be used at any step in the process of a systematic review for publication or as part of an assessment task. It provides valuable information to guide you whether you are new to conducting this type of review, but also if you want to improve and further develop your knowledge of systematic review requirements.
- Strech, D., & Sofaer, N. (2012). How to write a systematic review of reasons. Journal of Medical Ethics, 38(2), 121-126. doi:http://dx.doi.org/10.1136/medethics-2011-100096
- Cochrane, A. L. (1972). Effectiveness and efficiency : random reflections on health services. London]: London : Nuffield Provincial Hospitals Trust.
- Cochrane, A. L. (1979). 1931-1971: A critical review, with particular reference to the medical profession. In G. Teeling- Smith & N. Wells (Eds.).Medicines for the year 2000 (pp. 1-11). London: Office of Health Economics.
- Page, M. J., Shamseer, L., Altman, D. G., Tetzlaff, J., Sampson, M., Tricco, A. C., . . . Sarkis-Onofre, R. (2016). Epidemiology and reporting characteristics of systematic reviews of biomedical research: a cross-sectional study. PLoS medicine, 13(5). doi:http://dx.doi.org/10.1371/journal.pmed.1002028