magnitude of these effects are generally small, but the efforts that are generally more effective than other programs are implemented with high fidelity, focus on improving the capability of social organizations such as schools for managing themselves more effectively and communicating clear messages about expected behavior, and use cognitive-behavioral methods to teach skills that youths need to make competent decisions in social situations.

  • Considerable heterogeneity in effectiveness is found from study to study in each broad category of prevention activity. Although hints can be gleaned from the literature about factors that might differentiate the more effective from the less effective activities—such as duration, timing, and characteristics of the deliverer—existing research is not capable of isolating these moderating factors.

  • Some of the most widely promulgated classroom-based drug prevention programs—such as D.A.R.E. in the 1980s and early 1990s—have been found to have little impact on student drug use. Large amounts of public funds have been and continue to be allocated to prevention activities whose effectiveness is unknown or known to be limited.

  • It is not clear that preventing or reducing the use of gateway substances translates into reduced risk of use of cocaine or other illegal drugs. With only a few exceptions, the long-term effects of prevention programs are unknown.

  • Some evidence suggests that universal approaches to prevention of drug use have differential effects on different groups, so that students who have already initiated drug use before exposure to the program may escalate it following the program.

In light of these observations, the committee recommends a major increase in current efforts to evaluate drug prevention efforts. Further research is needed to better understand (1) effects of the entire spectrum of plausible approaches to prevention proposed or in use, rather than those that are most easily evaluated; (2) effects of drug prevention programs implemented under conditions of normal practice, outside the boundaries of the initial tightly controlled experimental tests of program efficacy under optimal conditions; (3) effects of different combinations of prevention programs, for example, how they complement each other or detract from one another when used in combination, as they most often are; and (4) the extent to which experimentally induced delays in tobacco, alcohol, and marijuana use yield reductions in later involvement with cocaine and other illegal drugs specifically, and long-term effects of prevention programming more generally.

Until the results of such research are available, policy makers have only a weak information base on which to base policy decisions and are

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