Two-year follow-up of a social-cognitive intervention to prevent substance use.

This study presents two-year follow-up results of the Adolescent Decision-Making Program initially implemented when students were in their sixth grade. The intervention was found to maintain a positive effect on mean tobacco use, but no differences were observed for mean alcohol, marijuana, or hard drug use. In a test of the differential effectiveness of the intervention, program students living with married parents reported lower mean tobacco use than control students living with married parents and program and control students living with single parents. Logistic regression analyses examining the proportion of users at follow-up revealed a negative program effect for alcohol and no differences for the other substances. Subsequent attrition analyses strongly suggested that the positive effect for tobacco use at follow-up was most likely even stronger, and that the negative effect for alcohol was spurious. The importance of examining both program and attrition effects when evaluating the impact of longitudinal preventive interventions was emphasized, and the need to consider alternative models to guide the conceptualization and evaluation of adolescent substance use prevention programs was discussed.