Clinical trials often aggregate daily alcohol consumption data across long-term follow-up intervals (e.g., 6 or 12 months). Although important in understanding general treatment outcomes, these analyses tell us little about when treatment effects emerge or decline. We previously demonstrated that motivational interviewing (MI) reduced heavy drinking (vs. personalized feedback only; FO) among young adult drinkers (N = 198; ages 18-24) recruited in a hospital Emergency Room (ER) using aggregated drinking data from 6-month follow up. In the current study, we used daily alcohol consumption data from a calendar-assisted interview (Timeline Followback) to examine the timing and course of these treatment effects. Participants in both conditions received brief telephone booster sessions at 1 and 3 months. There were no treatment effects in the time between the initial intervention session and the 3-month booster session. Significant effects emerged after the 3-month booster and were driven by an increase in heavy drinking within the FO group. This suggests that the effects of brief interventions may not emerge immediately following an initial session. Aggregated data would be unable to detect this time trend. This research underscores the potential value added by examining the day-to-day timing of effects following treatments for alcohol use.
Keywords: Daily Drinking, Timeline Followback, Motivational Interviewing, Screening and Brief Intervention, Young Adult