Aims: To systematically investigate the effectiveness of voucher-based reinforcement therapy for the treatment of substance use disorders.
Methods: Effect sizes and 95% confidence intervals were calculated for studies published between January 1991 and March 2004 that utilized voucher-based reinforcement therapy (VBRT) or related monetary-based incentives to treat substance use disorders (SUDs).
Findings: Thirty studies involved interventions targeting abstinence from drug use using experimental designs where effects on treatment outcome could be attributed to the VBRT intervention. The estimated average effect size (r) for those studies was 0.32 (95% CI 0.26-0.38). Analyses of variables thought to moderate VBRT effect sizes revealed that more immediate voucher delivery and greater monetary value of the voucher were associated with larger effect sizes. Additional studies were identified wherein VBRT was used to target clinic attendance (n = 6) or medication compliance (n = 4). VBRT studies targeting attendance produced average effect sizes of 0.15 (95% CI 0.02-0.28), while those that targeted medication compliance produced an average effect of 0.32 (95% CI 0.15-0.47). No significant moderators were identified for these 10 studies.
Conclusions: Overall, VBRT generated significantly better outcomes than did control treatments. These results further support the efficacy of VBRT, quantify the magnitude of its effects, identify significant moderators and suggest potential directions for future research.