The overall goal of this research is to improve treatment outcome for marijuana-dependent individuals. We propose to build on the positive findings of the Marijuana Treatment Project which demonstrated the efficacy of an intervention combining two sessions of motivational enhancement therapy with seven sessions of cognitive-behavioral coping skills therapy (MET/CBT). To enhance abstinence over the levels obtained in the prior study, a contingency management procedure will be added to the MET/CBT intervention, providing voucher-based reinforcement for abstinence. This combined intervention will be compared to MET/CBT-only and to contingency-management-only conditions, and to a control group that receives only case management. Recruitment of 248 marijuana-dependent participants will occur over a three-year period. They will be randomly assigned to one of the four 9-session interventions. Treatment will be individual, manualized, and provided on an outpatient basis. Comprehensive pretreatment assessments will provide baseline data against which to compare treatment outcomes. Follow-up assessments, at three-month intervals for one year following treatment, will evaluate marijuana and other drug/alcohol use, and psychosocial functioning in several domains. It is anticipated that the intervention combining contingency management and CBT/MET will result in the best outcomes, and that the contingency management and CBT/MET interventions by themselves will be superior to case management. Data will also be collected to enable study of the processes by which the interventions result in behavior change.
