Willpower versus "skillpower": Examining how self-efficacy works in treatment for marijuana dependence.

Self-efficacy has repeatedly been demonstrated to be a robust predictor of outcomes in the treatment of marijuana use disorders. It is not clear, however, how increases in confidence in ability to refrain from use get translated into actual improvements in drug-related outcomes. Marlatt, among others, viewed the acquisition and use of coping skills as the key to behavior change, and self-efficacy as a cognitive state that enabled coping. But that model of behavior change has not been supported, and few studies have shown that the effects of self-efficacy are mediated by coping or by other processes. The current study combined 3 marijuana treatment trials comprising 901 patients to examine the relationships between self-efficacy, coping, and potential mediators, to determine if the effects of self-efficacy on outcomes could be explained. Results of multilevel models indicated that self-efficacy was a strong predictor of adaptive outcomes in all trials, even when no active treatment was provided. Tests of mediation showed that effects of self-efficacy on marijuana use and on marijuana-related problems were partially mediated by use of coping skills and by reductions in emotional distress, but that direct effects of self-efficacy remained largely unexplained. The results are seen as supportive of efforts to improve coping skills and reduce distress in marijuana treatment, but also suggest that additional research is required to discover what is actually occurring when substance use changes, and how self-efficacy enables those changes.