Effects of varying the monetary value of voucher‐based incentives on abstinence achieved during and following treatment among cocaine‐dependent outpatients

Abstract

This study examined whether increasing the amount of abstinence achieved during outpatient treatment for cocaine dependence is an effective method for increasing longer-term cocaine abstinence. A two-condition, parallel groups, randomized controlled trial was conducted. The trial was conducted in a university-based research clinic. A total of 100 cocaine-dependent outpatients participated in the trial. Participants were assigned randomly to receive treatment based on the community reinforcement approach (CRA) plus voucher-based incentives set at a relatively high monetary value (maximal value = $1995/12 weeks) or CRA with vouchers set at a relatively low monetary value (maximal value = $499/12 weeks). Vouchers were earned contingent on cocaine-negative urinalysis results during the initial 12 weeks of the 24-week outpatient treatment. Outcomes were evaluated using urine-toxicology testing, questionnaires and other self-report instruments. Increasing voucher value increased the duration of continuous cocaine abstinence achieved during the 24-week treatment period. Point-prevalence cocaine abstinence assessed every 3 months throughout an 18-month follow-up period was greater in the high- than low-value voucher conditions. The duration of abstinence achieved during treatment predicted abstinence during follow-up, although that relationship weakened over time. Increasing the value of abstinence-contingent incentives during the initial weeks of treatment appears to represent an effective method for increasing during-treatment and longer-term cocaine abstinence, but the positive association of during-treatment abstinence with longer-term outcome dissipates with time.