Maximizing the Efficacy of Cognitive Behavior Therapy and Contingency Management

The investigators propose to evaluate targeted strategies to maximize the effectiveness of CBT and CM, respectively. To maximize the effectiveness of CBT, the investigators will evaluate the benefit of adding CM, with reinforcement for session attendance and homework completion, to standard individual CBT for outpatient marijuana abusers, in order to expose participants to more skill training and opportunities for practice of skills. To maximize the effectiveness and durability of CM, we will evaluate the benefit of integrating it with skills training, specifically designed to reduce drop off effects, in order to extend CM\'s benefits beyond the active treatment period. We propose to conduct a Stage II trial which will: (1) Evaluate the efficacy of four conditions for 160 marijuana dependent outpatients: (a) Standard CBT, (b) CBT with CM reinforcement for attendance and completing homework (CBT+CM/adherence), (c) CM for abstinence alone (CM/abstinence), (d) CM for abstinence integrated with CBT (CM/abstinence+CBT), and (2) Evaluate the longer-term durability and / or delayed emergence of treatment effects after termination of the study treatments through a one-year follow-up. Secondary aims will be to conduct (a) detailed process studies to evaluate whether the proposed enhancements affect proximal and distal outcomes as hypothesized and (b) economic analyses. Study treatments will last 12 weeks.