Motivational interviewing (MI) is an effective treatment for substance use disorders (SUDs) that focuses on resolving ambivalence and increasing commitment to positive behavior change. Although MI has a well-developed clinical theory, research findings have been mixed in supporting its view of how change occurs. The primary aim of this pilot study was to test hypothesized MI active ingredients and mechanisms of change in reducing drinking during the initiation of a behavior change episode. Problem drinkers (N = 89) seeking treatment were randomly assigned to MI, relational MI without directive elements (spirit-only MI [SOMI]), or a self-change (SC) control condition. Participants were followed during an 8-week treatment period. The first 2 of 4 treatment sessions were videotaped and coded for fidelity, discriminability, and change talk. Overall, conditions demonstrated high fidelity. As predicted, change talk significantly increased in MI relative to the SOMI condition. Drinking was significantly reduced at end treatment, but the reduction was equivalent across conditions. Post hoc analyses found that MI reduced drinking more rapidly than SOMI and SC and that increased change talk mediated the effects of MI relative to SOMI during the week immediately following the first session. Findings are discussed in the context of the pilot nature of the study and the relative absence of experimental tests of mechanisms of behavior change in SUD treatment research.
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