Comparison 9. Effect modification subgroup analysis: placebo as add‐on treatment.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Add‐on treatment: yes	17	1912	Risk Ratio (M‐H, Random, 95% CI)	0.96 [0.85, 1.07]
2 Add‐on treatment: no or not stated	27	4129	Risk Ratio (M‐H, Random, 95% CI)	0.94 [0.89, 1.00]
3 Add‐on treatment: yes	71	5423	Std. Mean Difference (IV, Random, 95% CI)	‐0.23 [‐0.31, ‐0.15]
4 Add‐on treatment: no or not stated	87	5090	Std. Mean Difference (IV, Random, 95% CI)	‐0.22 [‐0.30, ‐0.14]