App-Based Coaching to Prevent Addictive Behaviors in Vocational School Students: A Cluster Randomized Trial

This two-arm cluster randomized controlled trial evaluated the effectiveness of an app-based addiction prevention program in German vocational school students.

Schools from 5 German federal states were recruited. No eligibility criteria for classes were applied; enrollment decisions were made by school heads or teachers. Students were eligible if aged at least 16 years and possessing a smartphone (participation rate: 46.7%). Classes were randomly allocated to intervention or control within blocks of 4, stratified by school. Intervention classes received app-based coaching for 16 weeks. Control classes received health information and could access the coaching after 12 months. Both groups were assessed at baseline, 6 months, 6 and 12 months (follow-up rates: 35.8% and 34.9%). Primary outcomes were changes in alcohol, tobacco, cannabis consumption, and problematic Internet use at the individual level. Participants were blinded to group allocation until providing informed consent; the primary outcome analyst was also blinded. Generalized linear models with multiple imputation were used across all time points.

Intention-to-treat analyses of 1,266 intervention and 1,279 control participants from 162 classes each showed small but significant effects on social competence (b = 0.075, confidence interval [CI] 0.027, 0.123; d_6-months = 0.10; d_12-months = 0.19), stress (b = -0.02, [CI -0.03, -0.01]; d_6-months = -0.10; d_12-months = -0.20), problematic Internet use (b = -0.058, [CI -0.098, -0.019]; d_6-months = -0.08; d_12-months = -0.17), and tobacco consumption (b = -0.031, [CI -0.053, -0.009]).

App-based programs can reduce addictive behaviors and enhance life skills among vocational students, fostering broader mental health benefits.