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

Abstract

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 cognitive-behavioral therapy (CBT) via greater exposure to skills training; CBT was used as a strategy to enhance durability of CM with rewards for abstinence. Community-based out-patient treatment program in New Haven, Connecticut, USA. 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. 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). Weekly urine specimens testing positive for cannabis, days of cannabis use via the time-line follow-back method. 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. Combining contingency management and cognitive-behavioural therapy does not appear to improve success rates of treatment for cannabis dependence in clients involved with the criminal justice system.