Comparison 11. Risk of bias subgroup analysis: blinding of observer.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Blinding of observer: yes	2	316	Risk Ratio (M‐H, Random, 95% CI)	0.85 [0.68, 1.07]
2 Blinding of observer: not stated	11	1679	Risk Ratio (M‐H, Random, 95% CI)	0.96 [0.87, 1.06]
3 Blinding of observer: yes	20	669	Std. Mean Difference (IV, Random, 95% CI)	‐0.23 [‐0.42, ‐0.05]
4 Blinding of observer: not stated	29	1844	Std. Mean Difference (IV, Random, 95% CI)	‐0.07 [‐0.20, 0.06]