8. AMSTAR ratings.

AMSTAR Criteria	Cates 2008	Cates 2012a	Cates 2009a	Cates 2009b	Cates 2012b	Cates 2010
1. Was an 'a priori' design provided?	Yes	Yes	Yes	Yes	Yes	Yes
2a. Was there duplicate study selection? (0.5 point)	Yes	Yes	Yes	Yes	Yes	No
2b. Was there duplicate data extraction? (0.5 point)	No	No	Yes	Yes	Yes	No
3. Was a comprehensive literature search performed?	Yes	Yes	Yes	Yes	Yes	Yes
4. Was the status of publication (i.e. grey literature) used as an inclusion criterion?	No	No	No	No	No	No
5. Was a list of studies (included and excluded) provided?	Yes	Yes	Yes	Yes	Yes	Yes
6. Were the characteristics of the included studies provided?	Yes	Yes	Yes	Yes	Yes	Yes
7. Was the scientific quality of the included studies assessed and documented?	Yes	Yes	Yes	Yes	Yes	Yes
8. Was the scientific quality of the included studies used appropriately in formulating conclusions?	Yes	Yes	Yes	Yes	Yes	Yes
9. Were the methods used to combine the findings of studies appropriate?	Yes	Yes	Yes	Yes	Yes	Yes
10. Was the likelihood of publication bias assessed?	Yes	Yes	Yes	Yes	Not applicable	Not applicable
11. Was the conflict of interest stated?	Yes	Yes	Yes	Yes	Yes	Yes
Total criteria met:	10.5	10.5	11	11	10	9
(item 4 is met with the assessment 'NO', all others 'YES')
Note: we felt that item 2 was 2 separate questions, so we split it into two parts and awarded half a point for each. This differs from the published version of the tool.