1996; Gottfredson, 1986; Johnson et al., 1990; MacKinnon et al., 1991; Pentz et al., 1990; Pentz et al., 1989; Gottfredson et al., 1996; Skroban et al., 1999). Some of these attempts have been successful, and some have not. The less successful ones have suffered from implementation problems that may have been related to the multimodal nature of the program (e.g., Skroban et al., 1999). These individual studies have not resulted in an accumulation of knowledge about the conditions under which multimodal programs can work and the modes that can and cannot easily be combined. This line of inquiry will have to be carefully designed to control for conditions that may bear on the effectiveness of the activity.

Research should also test the interactive effects of the different elements. That is, combinations may increase the magnitude of effects through the additive effects of each component, but they may also have a multiplicative effect, so that certain strategies are more or less effective in combination with another than they are by themselves. For example, a drug prevention curriculum with a “no use” message may be counterproductive when delivered in a school environment in which norms favor use, or one in which the rules related to the possession of substances are lax or inconsistently applied. Only through research on the additive and multiplicative effects of different strategies can knowledge accumulate that will allow communities to develop portfolios of effective prevention strategies.

CONCLUSIONS AND RECOMMENDATIONS

A wide spectrum of plausible approaches to the prevention of substance use exist in both theory and practice. The effectiveness of most of these approaches for reducing substance use is unknown because the research evidence is nonexistent or inconclusive. Some of the approaches for which we have no evidence of effectiveness include many popular control strategies, such as zero-tolerance policies, the use of security measures such as locker searches, and the presence of police in schools, as well as more innovative approaches that draw on advances in toxicology, molecular biology, genetics, and clinical medicine (e.g., parents’ attempts to protect their children via increased use of home test kits to detect drug use, or active immunization of high-risk children with vaccine analogues). Research is needed on a wider array of prevention activities than has been studied to date.

With respect to the prevention approaches that have been studied, the committee makes the following observations:

  • Some prevention approaches are effective at delaying the initiation or reducing the frequency of tobacco, alcohol, and marijuana use. The



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