How do school-based drug prevention programs work and for whom?

School-based drug prevention programs focused on counteracting social influences to use cigarettes are the most effec- tive to date. However, the exact process by which effective pro- grams work remains unclear. This is due to the failure of program evaluations to include measures of mediating variables and to test for mediational processes. Available evidence suggests that a change in the social environment to one that is less tolerant of drug use is a likely mediator of program effects. There is inconsistent evidence that program effects differ by moderating variables such as gender, ethnicity, grade, socioeconomic status, and urbanization. Results from the few available studies suggest that both high-risk groups and more typical groups benefit from prevention programs. Analysis of mediation and moderation generate detailed information about how and for whom prevention programs work. As the field of school-based drug prevention research matures, mediating and mod- erating variables should receive increased attention.