Treatment for Adolescent Marijuana Abuse

Marijuana remains the most prevalent illicit substance used by adolescents and the number of
adolescents receiving treatment for marijuana abuse more than tripled during the last
decade. A small number of clinical trials suggest that family-based and individual
interventions have efficacy for treating adolescent substance abuse. However, even with
these interventions most adolescents fail to reduce their substance use substantially, thus,
there remains much room for improvement of treatment services. The overarching goal of this
project is to develop and test novel behavioral treatments to enhance treatment outcome in
this important treatment population, and in so doing, learn more about mechanisms of change
that have broader implications for addiction science. In our initial Stage IB project
"Behavioral Treatment for Adolescent Marijuana Abuse", we created, manualized, and pilot
tested a unique contingency-management (CM) intervention that combined abstinence-based
voucher incentives with contingency management training for parents. A small randomized,
clinical trial provided encouraging results. When added to a commonly used
cognitive-behavior therapy, CM improved rates of sustained abstinence during treatment.
Adolescents receiving this intervention were less likely to relapse over the 9-month
follow-up period, however this finding was not as robust as the observed during treatment
effects, most likely due to the small sample size and associated low power to detect
effects. Despite strong indicators of the efficacy of this CM intervention, there remained
room for improvement in increasing rates of treatment response and reducing rates of
relapse. Hypothesized mediators and moderators of change indicated that changes in parenting
had direct effects on post-treatment marijuana abstinence outcomes, and that abstinence
early in treatment was a robust predictor of the CM treatment effect. This proposal will
systematically replicate and extend these findings. A Stage II trial will compare three
treatment conditions: (1) cognitive behavior therapy (CBT only); (2) CBT plus CM; and (3)
CBT plus an enhanced CM model targeting increased early abstinence rates, parenting skills,
and maintenance of effects. Replicating the initial demonstration of the positive effects of
CM will extend the scientific evidence for use of CM to increase treatment efficacy for
substance-abusing adolescents. Testing an enhanced CM model will determine if modifications
that are consistent with the underlying behavioral principles and empiricism supporting CM
interventions can result in improved outcomes. Last, assessment of potential mechanisms of
action, particularly parenting, adolescent psychopathology and impulsivity, will provide
scientific information directly relevant to future development of more effective
intervention and prevention models of adolescent substance abuse, and will inform us about
fundamental mechanisms operating in drug-dependence.