Comparison 2. MI versus treatment as usual.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Extent of substance use	11		Std. Mean Difference (Random, 95% CI)	Subtotals only
1.1 Post‐intervention	9	1940	Std. Mean Difference (Random, 95% CI)	0.01 [‐0.09, 0.11]
1.2 Short f‐u	10	2102	Std. Mean Difference (Random, 95% CI)	0.01 [‐0.08, 0.10]
1.3 Medium f‐u	5	890	Std. Mean Difference (Random, 95% CI)	0.08 [‐0.05, 0.21]
2 Retention in treatment	4	1354	Std. Mean Difference (Random, 95% CI)	‐0.11 [‐0.41, 0.19]