Voucher-based contingent reinforcement of marijuana abstinence among individuals with serious mental illness

Previous studies by our group have used money given contingent on abstinence to reduce drug use by individuals with schizophrenia. In this study, we examined the sensitivity of marijuana use by individuals with serious mental illness to voucher-based contingent reinforcement, which represents the first study to date investigating the efficacy of voucher incentives with this population. This within-subject reversal design consisted of three conditions: 4-week baseline, 12-week voucher intervention, and 4-week baseline. During baseline periods, subjects received US$10 vouchers per urine specimen, independent of urinalysis results. During voucher intervention, only specimens testing negative for marijuana earned vouchers, with total possible earnings of US$930. Seven adults with schizophrenia or other serious mental illnesses participated in the study. The percentage of marijuana-negative specimens was significantly greater during voucher intervention than during baseline periods. These results provide evidence that marijuana use among individuals with serious mental illness is sensitive to voucher-based incentives and further support the potential feasibility of using voucher-based contingency management to reduce substance abuse in this challenging population.