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Keywords:

  • Cannabis dependence;
  • cognitive behavioral therapy;
  • contingency management;
  • criminal justice system;
  • randomized clinical trial

ABSTRACT

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 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.

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 cognitive–behavioural therapy does not appear to improve success rates of treatment for cannabis dependence in clients involved with the criminal justice system.