What we can--and cannot--expect from school-based drug prevention.

School-based drug prevention is a central component of drug control strategies. This paper assesses quantitatively its contributions in the United States from a social policy perspective. The social benefits per participant stemming from reduced drug use ( approximately $840 from tobacco, alcohol, cocaine and marijuana) appear to exceed the economic costs of running the programs ( approximately $150 per participant); while the benefits associated with reduced cocaine use alone ( approximately $300) exceed the costs, the corresponding figure for marijuana ( approximately $20) is small. Even if prevention reduced the use of other illicit drugs (e.g. heroin) by as much as it reduced use of cocaine, the majority of benefits would still stem from reductions in use of tobacco and alcohol, which has implications for how school-based drug prevention is funded and whether it is perceived more as a weapon in the war on illicit drugs or as a public health measure. Specific numeric results are subject to considerable uncertainty, but the basic character of the conclusions appears to be robust with respect to parameter uncertainty. The greatest uncertainties concern the permanence of prevention's effects and how to value instances of initiation being deferred but not completely prevented.