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.