Applied Social Sciences Index and Abstracts (ASSIA) (ProQuest) 1987 to present

CINAHL (EBSCOhost) 1981 to present

Cochrane Central Register of Controlled Trials (Wiley): Issue 4 of 12, April 2020

Cochrane Database of Systematic Reviews (Wiley): Issue 4 of 12, April 2020

EMBASE Classic+EMBASE (Ovid) 1947 to 27 April 2020

Ovid MEDLINE(R) and Epub Ahead of Print, In-Process & Other Non-Indexed Citations and Daily 1946 to 28 April 2020

APA PsycINFO (Ovid) 1806 to April Week 3 2020

Web of Science Core Collection: Citation Indexes (Clarivate Analytics) 1900 to present

ISRCTN registry (Springer)

ClinicalTrials.gov (US National Institutes of Health)

Evidence Search (National Institute for Health and Care Excellence)