Exploration of treatment matching of problem drinker characteristics to motivational interviewing and non-directive client-centered psychotherapy.

Motivational Interviewing (MI) is a known effective intervention for alcohol use disorder (AUD). MI's mechanisms of action remain inconsistently substantiated, and research in this area has been reliant on identifying relationships through strength of association rather than experimental manipulation of active ingredients. In two previous studies, a pilot and a larger replication study, we disaggregated MI into its hypothesized active ingredients by creating three conditions: MI, Spirit Only MI (SOMI, in which evocation of change talk was proscribed), and a non-therapy condition (NTC). Results from both studies yielded equivalent findings across all three conditions. In the current analyses, data from both studies were combined to test five participant characteristics as moderators of MI's component parts: 1) severity of baseline drinking, 2) severe AUD (met 6 or more criteria), 3) baseline self-efficacy to moderate drinking, 4) mean daily confidence to resist heavy drinking in the week prior to treatment initiation, and 5) depression. There were no significant findings related to baseline drinking, severe AUD, or baseline self-efficacy. Confidence yielded a significant interaction effect. When participants had high baseline confidence, drinking for those in MI increased compared to those in SOMI. Depression also yielded a significant moderating effect such that in the context of higher depressive symptoms, receipt of either therapy reduced drinking relative to NTC. Results are discussed in light of existing literature on MOBC with MI and the potential role exploring ambivalence may play for participants with particular characteristics.