2.2. Database Search

This review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [17] and the Cochrane Handbook for Systematic Reviews of Interventions [18]. The following databases were searched for articles published until June 2020: MEDLINE (PubMed), Cochrane Central Register of Controlled Trials (CENTRAL), Excerpta Medica Database (EMBASE), China National Knowledge Infrastructure (CNKI), Oriental Medicine Advanced Searching Integrated System (OASIS), Korean Traditional Knowledge Portal (KTKP) and Citation Information by National Institute of Informatics (CiNii). In addition, a manual search was performed to search the reference lists of relevant articles and Google Scholar to identify further studies. The search strategies were modified for each database, and there was no language restriction when selecting studies. The detailed search strategy for each database is as in Appendix A.