Table 2.

The number of studies found per source across the various stages of the literature selection process.

Stage	Source	Remaining number of findings
Initial findings
	Scopus	55
	PubMed	36
	Web of Science	57
	Total	148
Removal of duplicates
	Scopus	54
	PubMed	29
	Web of Science	39
	Total	122 (26 duplicates removed)
Initial screening
	Total	20 (102 excluded)
Snowball method
	Total	27 (7 included)
In-depth quality assessment
	Total	24 (3 excluded)