have been hard to quantify, so economic research into these areas has been scant. Little is known about the incentives provided by legal and social sanctions aiming to deter drug use (discussed in Chapter 6). Moreover, economists have generally not considered environmental, family, or peer influence on drug use. Conversely, social psychologists have studied individual, family, peer, neighborhood, and social risk factors for drug use but have generally neglected the economic costs of using drugs.

The first section of this chapter summarizes what is known about the determinants of drug use and describes methodological and data-related problems in evaluating these determinants. It begins with a review of the neuroscience perspective, with an emphasis on how the effects of drug use vary across drugs, individuals, and their circumstances. It then examines economic research on the price sensitivity of drug use. Finally, it summarizes what is known about how individual and social factors may influence drug use.

This survey is intentionally brief. The literature on the determinants of drug use is enormous in volume and scope. Researchers in criminology, economics, sociology, psychology, biochemistry, neurobiology, and epidemiology have sought to understand the determinants of illegal drug use. Since a comprehensive survey of this large literature is beyond the purview of this report, this section attempts to summarize key features of the knowledge base that may be important to evaluate the effectiveness of drug control policies. For a contemporary and more comprehensive review of what is known about the addictive process, see the recent Institute of Medicine reports, Pathways of Addiction (1996) and Dispelling the Myths About Addiction (1997).

The Neuroscience Perspective on Addiction

Many medical researchers view addiction as a disease similar to other chronic and relapsing conditions, such as asthma, diabetes, and hypertension (Institute of Medicine, 1995, 1996, 1997; O’Brien and McLellan, 1996; Leshner, 1997). According to this perspective, the physical dependence created by some drugs plays a relatively minor role. Treating the pain and suffering that starts when drug use stops is straightforward, while effective intervention to prevent relapse into drug-taking is quite complex. Long-term changes to the brain circuitry and the emotional cues that can trigger this circuitry may last a lifetime (Institute of Medicine, 1997). As with any chronic relapsing disease, understanding the dynamic processes of initiation, escalation, reduction, persistence, and relapse are especially important and difficult challenges. The processes that affect initiation of drug use are not identical to those that promote persistence of drug use or development of drug dependence (e.g., see Tsuang et al., 1999; Stallings et



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