Traditional literature reviews are prone to bias in various ways. Authors may choose to only include studies with which they are familiar or which support their point of view - this is known as selection bias (or ‘file-drawer bias’). Authors may choose to include only published studies (publication bias) or only studies written in English (language bias). Limiting searches to certain databases and indexing terms may also introduce bias into the review.
A systematic review is more rigorous and attempts to reduce the influence of bias in the following ways:
How to conduct a Cochrane systematic review
- It addresses a clearly formulated question.
- It uses systematic and explicit methods to identify, select and critically appraise relevant research.
- It uses systematic methods to collect and analyse data from the studies included in the review.
- Statistical methods (meta-analysis) may or may not be used to analyse and summarise the results of included studies which are considered similar enough to combine.
When one decides to do a review, the first step is to contact the relevant Review Group Managing Editor (http://www.cochrane.org/contact/review-groups) to register the topic. The next stage involves developing a protocol which must be peer-reviewed before you can begin the review.
see the attached diagram for an outline of the review process.
Cochrane SA can assist you with the stages of this process and will put you in touch with the right people.
How long does it take?
A review takes 18 months on average. Once you have published a review, you are responsible for updating it every two years - your Review Group will assist you in this process.
What's in it for me?
A full review is indexed on MEDLINE. In 2013 the Cochrane Database of Systematic Reviews received an impact factor of 5.939.
Once you have published a review you will automatically receive your own free copy of The Cochrane Library as long as it is updated regularly.