Objective: The purpose of the present study was to develop a treatment for marijuana dependence specifically designed to enhance self-efficacy.
Method: The participants were 215 marijuana-dependent men and women randomized to one of three 9-week outpatient treatments: a condition intended to enhance self-efficacy through successful completion of treatment-related tasks (motivational enhancement plus cognitive-behavioral treatment plus contingency management reinforcing completion of treatment homework; MET + CBT + CM[Homework]); a condition that controlled for all elements except for reinforcement of homework (MET + CBT + contingency management reinforcing drug abstinence; MET + CBT + CM[Abstinence]); or a case management control condition (CaseM). Participants in the two MET + CBT conditions were also asked to complete interactive voice recordings three times per week during treatment to confirm homework completion.
Results: All patients showed modest improvements over time through 14 months, with few between-treatment effects on outcomes. Latent Class Growth Models, however, indicated that a subsample of patients did extremely well over time. This subsample was more likely to have been treated in the CMAbstinence condition. In turn, this treatment effect appears to have been accounted for by days of continuous abstinence accrued during treatment, and by pre-post increases in self-efficacy.
Conclusions: The most effective treatments may be those that elicit abstinence while increasing self-efficacy.

Highlights:
Marijuana is the most used drug in the US, and achieving abstinence is difficult.
Contingency management and self-efficacy based treatments have been most effective.
We sought to enhance self-efficacy by reinforcing completed treatment assignments.
Results showed that a treatment reinforcing abstinence was slightly more effective.
Analyses indicated that initial abstinence and self-efficacy best predicted outcome.