quences of drug-taking and possibly initiation and continuation of use (Institute of Medicine, 1996, 1997). Studies of families show that children of alcoholics are at much higher risk of developing the disorder even if adopted at birth and raised by nonalcoholic adoptive parents. Studies of twins and adopted children suggest that early onset of alcoholism is strongly influenced by genetic factors, while later onset seems more strongly influenced by environmental and emotional factors. Some Asians with a specific genotype are biologically protected from becoming alcoholics. Caucasians are not known to have this genotype, but there is evidence of genetic influence on early tolerance to alcohol and with it an increased vulnerability to alcoholism (Institute of Medicine, 1996; Yoshida et al., 1991). Animal studies have demonstrated strong genetic influences over both use and intensification, and while specific genes and combinations of genes have not yet been identified, there is evidence for the inheritance of a variety of alcohol-related traits, including preference, sensitivity, tolerance, and withdrawal (e.g., see Argawal and Goedde, 1990; Yoshida et al., 1991; Uhl et al., 1995; Institute of Medicine, 1996, 1997; Merikangas et al., 1998b; Tsuang et al., 1998; Kendler and Gardner, 1998; Kendler and Prescott, 1998a, 1998b; Foroud and Li, 1999; Adams et al., 1999; Uhl, 1999; True et al., 1999; Kendler et al., 1999; Sellers and Tyndale, 2000).

In addition to individual risk factors, social factors may also play an important role. Sociologists and social psychologists have long sought to determine how social interactions and environment more generally may affect drug use. Suggestive statistical associations have frequently been reported. Risk-associated characteristics of families and communities, which may be constant (e.g., multigenerational family history of drug dependence), or time-varying conditions (e.g., harmful processes of abusive or coercive social interaction within families) are related to subsequent use. Children of addicts are more likely than their counterparts to use and abuse drugs as adults. Neighborhood and community drug use patterns and crime rates are correlated with use (Luthar and Cushing, 1999; Petronis and Anthony, 2000). Association with substance-using peers is also highly predictive of substance use. Adolescent use generally takes place among peers and most individuals also experience some peer influence to use drugs (Van Etten et al., 1997; Van Etten and Anthony, 1999).

Of course, social factors may be associated with less drug use. The costs of use are higher for people who have greater stakes in conformity, who care about maintaining the respect of people to whom they are attached, and who care about the investments they have made in their futures. In control theory terminology, individuals with weak bonds to society are more likely to engage in risky, harmful, or criminal behaviors



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