The lack of suitable data is the most serious obstacle to developing better demand functions and estimates of price elasticities. It is unlikely that significantly better estimates can be developed without better data on retail prices, quantities transacted and consumed, and search costs. Improved data on quantities and search costs will be most useful if they are longitudinal. Without reliable price and consumption data, it is not possible to predict the outcomes of policy measures aimed at influencing the price or availability of illegal drugs, and it is not possible to evaluate the effects of these policies after they have been implemented.

Individual and Social Risk Factors

Some research explores the statistical association of drug use with risk factors, which characterize individuals or their environment. Risk factors are conditions and processes that, when present, signal an increased likelihood that individuals will develop a behavior or a health-related condition (Garmezy, 1983).8 A large literature provides a wealth of information on the risk factors associated with drug use: children growing up with addicted parents are more likely to use and abuse, deviant adolescents are more likely to use as adults, individuals residing in high-crime areas are more likely to use, etc. These and other risk factors are sometimes taken to be “candidate causes” of drug use—suspected causal influences for which there may not be enough evidence to make a firm claim of causation.

Other risk factors, in contrast, signal a reduced likelihood of a behavior or condition, such as drug use or drug dependence. Some are thought to act by offering direct resistance to ill health or maladaptation. The gene-linked enzymes involved in alcohol and nicotine metabolism, which encourage drowsiness or another symptom that discourages further use, are of this type. Others are thought to act by canceling or modifying the negative effects of risk-increasing factors. For example, frequent participation in church-related activities may reduce the risks associated with living in neighborhoods with street-level drug markets (Crum et al., 1996). Some may directly reduce a dysfunction, lessen the effect of the risk-increasing factors, disrupt the process through which certain factors operate to cause a dysfunction, or prevent the initial occurrence of deleterious factors (Coie et al., 1993).


In the prevention field, no single theoretical model has been embraced, although most organized prevention activities rely on a risk and protective factor framework (Van Etten and Anthony, 1999; Institute of Medicine, 1994). Hansen and O’Malley (1996) identify eight different theoretical models that have dominated prevention activities.

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