Effects of voucher-based intervention on abstinence and retention in an outpatient treatment for cocaine addiction: a randomized controlled trial.

The aims of this study were to assess whether voucher magnitude improved cocaine abstinence and retention in an outpatient treatment for cocaine dependence, and to determine the effectiveness of a contingency management intervention in a European cultural context. A randomized controlled trial was conducted in which 96 participants who were randomly assigned to 1 of 3 treatment conditions in a community setting: standard outpatient treatment, community reinforcement approach (CRA) plus low monetary value vouchers (each point earned was equivalent to 0.125 Euro, US$ 0.18), and CRA plus high monetary value vouchers (each point was worth 0.25 Euro, US$ 0.36). In the standard treatment group, mean percentage of cocaine-negative samples was 88.45%, versus 96.09% in the CRA plus low-vouchers group, and 97.07% in the CRA plus high-vouchers group. Retention rate at 6 months was 36.5% in the standard treatment group, 53.3% in the CRA plus low-vouchers group, and 69.0% in the CRA plus high-vouchers group. The CRA plus vouchers groups obtained better results than the standard program. This study showed that treating cocaine addiction by combining CRA with vouchers was more effective than standard treatment in community outpatient programs in Spain.