Prize-based contingency management for the treatment of substance abusers: A meta-analysis

Aim: To review randomized controlled trials to assess efficacy of a prize-based contingency management procedure in reducing substance use (where a drug-free breath or urine sample provides a chance of winning a prize). Methods: A meta-analysis was conducted on papers published from January 2000 to February 2013 to determine the effect size of studies comparing prize-based contingency management to a treatment-as-usual control condition (k=19 studies). Parallel analyses evaluated the efficacy of both short- (k=nine studies) and long-term outcomes (k=six studies) of prize-based contingency management. Results: The average end-of-treatment effect size (Cohen's d) was 0.46 [95% confidence interval (CI)=0.37, 0.54]. This effect size decreased at the short-term (≤3-month) post-intervention follow-up to 0.33 (95% CI=0.12, 0.54) and at the 6-month follow-up time-point there was no detectable effect [d=-0.09 (95% CI=-0.28, 0.10)]. Conclusion: Adding prize-based contingency management to behavioral support for substance use disorders can increase short-term abstinence, but the effect does not appear to persist to 6 months.