PubMed, Scopus and EBSCOhost databases (Academic Search Premiere, Computer and Applied Science complete, CINAHL, MEDLINE, APA PsychArticles, Psychology and Behavioural Sciences collection, APA PsychInfo) will be searched to identify eligible articles (from January 1990 onwards). 
PubMed
PubMed, Scopus and EBSCOhost databases (Academic Search Premiere, Computer and Applied Science complete, CINAHL, MEDLINE, APA PsychArticles, Psychology and Behavioural Sciences collection, APA PsychInfo) will be searched to identify eligible articles (from January 1990 onwards). 
Scopus
PubMed, Scopus and EBSCOhost databases (Academic Search Premiere, Computer and Applied Science complete, CINAHL, MEDLINE, APA PsychArticles, Psychology and Behavioural Sciences collection, APA PsychInfo) will be searched to identify eligible articles (from January 1990 onwards). 
EBSCOhost
Infomit and Google Scholar (limited to 200 results) will be searched for grey literature. 
Infomit
Infomit and Google Scholar (limited to 200 results) will be searched for grey literature. 
Google Scholar