Effect of anxiety on treatment presentation and outcome: results from the Marijuana Treatment Project

Abstract

Despite emerging evidence of the efficacy of psychotherapies for marijuana dependence, variability in outcome exists. This study examined the role of anxiety on treatment involvement and outcome. Four questions were examined: (1) Is greater anxiety associated with greater impairment at baseline? (2) Is baseline anxiety related to greater marijuana use and problems following treatment? (3) Does adding cognitive-behavioral therapy (CBT) to motivation enhancement therapy (MET) reduce anxiety relative to MET alone; (4) Are reductions in anxiety associated with better outcomes? The sample comprised 450 marijuana-dependent patients in the Marijuana Treatment Project. Marijuana use and anxiety were measured at pretreatment and 4- and 9-month follow-ups. At baseline, anxiety was linked to more marijuana-related problems. CBT was associated with less anxiety at follow-up compared to MET alone. Reductions in anxiety were related to less marijuana use. In fact, reduction in anxiety from baseline to 4-month follow-up was associated with less marijuana use at 9 months, but reduction in marijuana use did not predict subsequent anxiety. Data suggest that anxiety is an important variable that deserves further attention in marijuana-dependence treatment.

Figure 1

Structural equation models showing (1) relationship between change in anxiety from baseline to 4-month follow-up and marijuana use outcome and (2) relationship between change in marijuana use from baseline to 4-month follow-up and anxiety outcome. MET=motivation enhancement therapy. CBT=cognitive-behavior therapy.