Comparison 6. Effect modification subgroup analysis: the purpose of the trials.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 To study the effect of placebo was an explicit trial purpose	11	1163	Risk Ratio (M‐H, Random, 95% CI)	0.90 [0.78, 1.04]
2 To study the effect of placebo was not an explicit trial purpose	33	4878	Risk Ratio (M‐H, Random, 95% CI)	0.94 [0.88, 1.01]
3 To study the effect of placebo was an explicit trial purpose	28	2027	Std. Mean Difference (IV, Random, 95% CI)	‐0.34 [‐0.46, ‐0.22]
4 To study the effect of placebo was not an explicit trial purpose	130	8486	Std. Mean Difference (IV, Random, 95% CI)	‐0.20 [‐0.26, ‐0.14]