A systematic search to identify studies must be comprehensive and it must strike a balance between recall and precision. In other words, don't expect to retrieve only relevant articles.
Most studies used in the review will be identified using electronic databases (e.g. PubMed). But, The Cochrane Collaboration states that "efforts should be made to identify unpublished studies." (Cochrane Handbook 6.2.4) Librarians can help to identify sources for finding grey literature.
Expect a large number of results. Depending on the scope of your topic, your search may result in as few as a couple hundred or as many as several thousand articles.
Some key steps in searching for studies include:
It’s important to note that the National Academies of Sciences, Engineering and Medicine recommends working “with a librarian or other information specialist trained in performing systematic reviews to plan the search strategy” (Standard 3.1.1).
Librarians at the USF Health Libraries are expert searchers who can support faculty investigators in conducting comprehensive literature searches for systematic reviews, assist with reference management and writing the search methodology section of the review. Consider meeting with a librarian to discuss your systematic review project.