Information sources and search strategy

The protocol for comprehensive literature searches were developed by an experienced information specialist (JM) in consultation with the research team and completed by a library technician (AE). First, we searched MEDLINE, EMBASE, Education Resources Information Center (ERIC), PsycINFO, Joanna Briggs, the Cochrane Library, Evidence Based Medicine (EBM) Reviews, and the Campbell Library from 2005 to April 2016. Second, we searched for grey literature (i.e. difficult to locate or unpublished material) using the Canadian Agency for Drugs and Technologies in Health Grey Matters checklist [35]. Specifically, we searched Google and websites of funding agencies such as the CIHR, UK MRC and NIH. Third, we asked experts in the field to identify any additional potentially relevant articles. We limited the search to articles published in English. The final search strategy for MEDLINE is presented in S2 Appendix and additional search strategies are available from the corresponding author upon request.