Aims: The purpose of this systematic review was to determine if school-based marijuana and alcohol prevention programs are effective in preventing marijuana and alcohol use in adolescents between the ages of 10-15 years. In particular, we examined knowledge versus comprehensive type prevention programs in order to better understand the inconsistency of results in school-based marijuana and alcohol prevention programs found in the literature.
Methods: We performed a systematic literature review to identify published or unpublished papers between January 01, 1980 and December 02, 2007 that reviewed the long-term effectiveness (1 year or longer) of school-based marijuana and alcohol primary prevention programs targeting adolescents aged 10-15 years.
Results: Long-term marijuana and alcohol prevention programs that utilized a "comprehensive" program content resulted in: (a) a mean absolute reduction of 12 days of alcohol usage per month and (b) a mean absolute reduction of 7 days of marijuana usage per month among adolescents aged 10-15 years old. In comparison, school-based marijuana and alcohol prevention programs that utilized "knowledge only" program content resulted in a mean absolute decrease of 2 days of alcohol usage per month among adolescents aged 10-15 years old. Only one study used knowledge-based content and marijuana use as an outcome measure and as such statistical pooling was not possible.
Conclusions: The most effective primary prevention programs for reducing marijuana and alcohol use among adolescents aged 10-15 years in the long-term were comprehensive programs that included anti-drug information combined with refusal skills, self-management skills and social-skills training.