Three-Arm Randomized Controlled Trial of Motivational Interviewing for Adolescent Drinking in Denmark

OBJECTIVE: To test the effectiveness of group motivational interviewing (GMI) and school/parent intervention (SP) in reducing drinking among public high school students in Denmark, a region with high rates of hazardous alcohol use. METHOD: This was a 3-arm, cluster-randomized controlled trial in 16 public high schools block-randomized to the following: (1) 2-session, manualized GMI coupled with SP; (2) SP-only; or (3) assessment-only control. A total of 2,766 students (65.53% female; mean age = 16.77 years, range = 15-19 years) completed online surveys during class periods at baseline and at 2, 6, 9, and 12 months. The primary outcome was past-month peak drinks per occasion at 12-month follow-up. Mixed models estimated change from baseline for each condition and mean change difference across conditions. RESULTS: Students in the control condition significantly increased peak drinks over time at 2.5 times the rate of the other conditions (Δmean = 1.13 [95% CI = 0.62, 1.64] vs 0.48 [95% CI = 0.03, 0.93] for GMI+SP and 0.47 [95% CI = 0.06, 0.88] for SP-only). The mean change difference in peak drinks for each GMI+SP and SP-only vs control was significant (Δmean = -0.65 [95% CI = -1.28, -0.02] and -0.66 [95% CI = -1.27, -0.04], respectively), although significance did not persist after p value correction. More robust effects were observed for the secondary outcome of past-month total drinks. CONCLUSION: GMI coupled with school-based alcohol policies and parental education represents a promising approach to mitigating drinking among high school students. This study supports the crucial roles of developmentally salient relationships (eg, peers, parents/guardians) and contexts (eg, school, home) in developing and delivering intervention programs to adolescents. CLINICAL TRIAL REGISTRATION INFORMATION: Prevention of Hazardous Use of Alcohol with Danish High School Students (Our Choice); https://clinicaltrials.gov/study/NCT06018389?cond=NCT06018389.