Abstinence rates following behavioral treatments for marijuana dependence

Previous studies have noted particular difficulty in achieving abstinence among those who are marijuana dependent. The present study employed a dismantling design to determine whether adding contingency management (ContM) to motivational enhancement therapy plus cognitive behavioral therapy (MET + CBT), an intervention used in prior studies of treatment for marijuana dependence, would enhance abstinence outcomes. 240 marijuana dependent participants were recruited via advertisements and assigned to either MET + CBT, ContM-only, MET + CBT + ContM, or to a case-management control condition. All interventions involved 9 weekly 1-h sessions, except for the ContM-only condition whose sessions lasted about 15 min. ContM provided reinforcement for marijuana-free urine specimens, in the form of vouchers redeemable for goods or services. Follow-up data were collected at posttreatment and at 3-month intervals for 1 year. The two ContM conditions had superior abstinence outcomes: ContM-only had the highest abstinence rates at posttreatment, and the MET + CBT + ContM combination had the highest rates at later follow-ups. The roles of contingency management and coping skills training in the treatment of marijuana dependence are discussed.