Effectiveness of School-based Drug Prevention Programs for Marijuana Use.

Thirty-seven evaluations of universal drug use prevention programs implemented in American schools between grades 6 and 12 were quantitatively synthesized by coding program characteristics and calculating weighted effect sizes (WES) for marijuana use. Programs were divided into two types, Interactive and Non-Interactive, based on a combination of content and delivery method. To determine the characteristics of programs that most effectively reduce, delay or prevent marijuana use, a weighted least squares multiple regression analysis was performed using the WES of marijuana use as the dependent variable, type of program as the predictor and sample size as an additional covariate. Program type and sample size were found to be significant predictors of program effectiveness. Non-Interactive lecture-oriented prevention programs that stressed knowledge about drugs or affective development of students showed minimal reductions in marijuana use. Interactive programs that fostered the development of social compet...