Combining cognitive behavioral therapy and contingency management to enhance their effects in treating cannabis dependence: less can be more, more or less

Aims To evaluate reciprocal enhancement (combining treatments to offset their relative weaknesses) as a strategy to improve cannabis treatment outcomes. Contingency management (CM) with reinforcement for homework completion and session attendance was used as a strategy to enhance cognitivebehavioral therapy (CBT) via greater exposure to skills training; CBT was used as a strategy to enhance durability of CM with rewards for abstinence. Setting Community-based out-patient treatment program in New Haven, Connecticut, USA. Design Twelve-week randomized clinical trial of four treatment conditions: CM for abstinence alone or combined with CBT, CBT alone or combined with CM with rewards for CBT session attendance and homework completion. Participants A total of 127 treatment-seeking young adults (84.3% male, 81.1% minority, 93.7% referred by criminal justice system, average age 25.7 years). Measurements Weekly urine specimens testing positive for cannabis, days of cannabis use via the time-line follow-back method. Findings Within treatment, reinforcing homework and attendance did not significantly improve CBT outcomes, and the addition of CBT worsened outcomes when added to CM for abstinence (75.5 versus 57.1% cannabis-free urine specimens, F = 2.25, P = 0.02). The CM for abstinence condition had the lowest percentage of cannabis-negative urine specimens and the highest mean number of consecutive cannabis-free urine specimens (3.3, F = 2.33, P = 0.02). Attrition was higher in the CBT alone condition, but random effect regression analyses indicated this condition was associated with the greatest rate of change overall. Cannabis use during the 1-year follow-up increased most rapidly for the two enhanced groups. Conclusions Combining contingency management and cognitivebehavioural therapy does not appear to improve success rates of treatment for cannabis dependence in clients involved with the criminal justice system.