Table 1.

Results of database searches.

Source	Hits per strategy	Unique studies	Relevant studies
PubMed	388	388	11
Communication Abstracts	0	0	0
PsycINFO	47	40	0
EMBASE	169	82	0
Snowball method	3	0	1
CINAHL	13	10	1
Total	620	520	13