Long-term effects of a parent and student intervention on alcohol use in adolescents: A cluster randomized controlled trial

Background: Early onset of drinking among Dutch adolescents is highly prevalent. A lower age of onset is associated with several developmental and social risks. Purpose: To evaluate the long-term effectiveness of two preventive interventions targeting heavy drinking in third-year high school students. Design: Cluster RCT using four conditions for comparing two active interventions (separately and simultaneously) with a control group. Setting/participants: 152 classes of 19 high schools in the Netherlands; 3490 first-year high school students (M=12.6 years, SD=0.49) and their parents. Intervention: (1) parent intervention aimed at encouraging restrictive parental rule-setting concerning their children's alcohol consumption; (2) student intervention aimed at increasing self-control and healthy attitudes toward alcohol, consisting of four digital lessons based on the principles of the theory of planned behavior and social cognitive theory; (3) interventions 1 and 2 combined; and (4) the regular curriculum as control condition. Main outcome measures: Incidence of (heavy) weekly alcohol use at 34 months (2009) after baseline measurement (2006). Results: There were 2937 students eligible for analyses in this study. At follow-up, only the combined studentparent intervention showed substantial and significant effects on heavy weekly and weekly drinking. Conclusions: The short-term effects found in the present study further support that adolescents as well as their parents should be targeted in order to delay the onset of (heavy) drinking. Trial registration: NTR649. © 2011 American Journal of Preventive Medicine.