Comparison 19. Once‐only interventions (individual setting) vs waiting list.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
19.1 Secondary: impulsivity (continuous), at end of treatment	1		Mean Difference (IV, Fixed, 95% CI)	Subtotals only
19.2 Secondary: interpersonal problems (continuous), at end of treatment	1		Mean Difference (IV, Fixed, 95% CI)	Subtotals only
19.3 Secondary: attrition (dichotomous), at end of treatment	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only