Day-Level Mediators of Change in Brief Motivational Intervention for Alcohol Use and Liver Health

Background Day-level motivation to limit drinking is theorized to be a proximal mechanism of change in motivational interviewing (MI) interventions targeting alcohol intake, but day-level evidence remains limited. This study examined whether brief MI with personalized biobehavioral feedback was associated with changes in daily drinking among adults with alcohol use disorder (AUD) and alcohol-associated liver disease (ALD), and whether day-level importance and confidence to limit drinking served as within-person mediators of change. Methods Participants ( N =  33; M age = 46.0 (12.55); day-level observations = 799) completed morning surveys for 28 days, including up to 10 pre-intervention days. Multilevel interrupted time-series models partitioned intervention effects into pre-intervention slope, intervention-day level shift, and post-intervention slope, and tested whether the intervention’s effects on daily drinking were mediated by day-level importance and confidence to limit drinking. Results Daily drinking outcomes declined during the pre-intervention period, with no significant intervention-day shifts or post-intervention trends. However, the intervention-day shift was associated with increased day-level importance of limiting drinking, and higher-than-usual importance and confidence in limiting drinking on a given day were associated with fewer planned and actual drinks and lower odds of any drinking and heavy drinking. The intervention-day shift exerted significant indirect effects on daily drinking outcomes through same-day increases in importance of limiting drinking. Conclusions Intensive longitudinal data supported perceived importance of limiting drinking as a proximal day-level mediator of change in brief AUD/ALD interventions, suggesting that frequent, day-level reinforcement of the personal salience of drinking reduction may be a key intervention target.