The finding that self-efficacy was a major contributor to outcome was not unexpected on the basis of earlier work. Self-efficacy has been predictive of both short-term (1 year) and long-term (3 year) alcohol treatment outcomes (e.g., Greenfield et al., 2000; Project MATCH Research Group, 1997). In addition, however, self-efficacy in the present study appeared to be an important mediator of treatment effects. This finding is somewhat less common (Maisto, Connors & Zywiak, 2000; Witkiewitz & Marlatt, 2004), and bolsters the idea that self-efficacy is a major determinant of behavior change in alcohol treatment (see also Litt et al., 2003). This is similar to the finding of Morgenstern et al. (1997), which indicated that effects of AA on later drinking were mediated by self-efficacy. The fact that self-efficacy was a function of number of abstinent friends in the social network, suggests that social supports may be strengthening self-efficacy beliefs (e.g., Davis & Jason, 2005).
