Much of what is currently understood about the progression of adolescent alcohol and drug abuse comes from longitudinal studies of school samples. Such research implicates peer, family, sociocultural, and personality factors in the onset of drinking, heavy consumption, and later problems with alcohol and drugs. Evidence from longitudinal studies (e.g., Aarons et al., 1999; Kandel, Davies, Karus, & Yamaguchi, 1986; Newcomb & Bentler, 1988) also suggests that drug use during adolescence has important consequences during young adulthood, including delinquent behavior, physical and psychological disturbances, unstable work patterns, and higher divorce rates. Interestingly, drinking patterns may vary markedly from adolescence to young adulthood, and the consequences of alcohol consumption during adolescence appear to be less severe than that of hard drug use.

Although research utilizing school samples provides important information about adolescent substance use and its consequences, these studies may underestimate the true frequency and severity of the problem. Teens with the most disruptive alcohol and drug use patterns are underrepresented in school samples, as they often fail to attend school and experience frequent suspension or expulsion (e.g., Brown, Vik, & Creamer, 1989). Additionally, an early onset of drug and alcohol problems of sufficient severity to merit treatment suggests that there may be differences in the course of abuse or consequences for those entering treatment compared to teens who remain in school (Brown, Mott, & Myers, 1990). Keeping in mind these differences, the next section discusses major risk factors for adolescent alcohol and drug abuse. . .

Family, twin, and adoption studies document the importance of genetic factors in lifetime risk for alcohol dependence, especially in males (e.g., Schuckit, 1985). It has been argued (Cloninger, Bohman, & Sigvardsson, 1981) that the clinical course is different for adult alcoholics with a family history of alcoholism compared to alcoholics without such a family history. Family studies consistently find an elevated prevalence of alcohol dependence in the first-degree relatives of alcoholics (Sher, 1987). In a review of 39 studies, Cotton (1979) found that adult alcoholics were more than six times as likely as nonalcoholic nonpsychiatric individuals, and more than two times as likely as nonalcoholic psychiatric patients, to report parental alcoholism. Twin studies demonstrate a concordance of 60% or higher for the identical twin of an alcoholic but only 30% or less if the relationship is fraternal. Adoption studies (e.g., Cloninger et al., 1981; Goodwin et al., 1974) find a fourfold increased risk for lifetime alcoholism in offspring separated from their biological parents in infancy and raised without knowledge of the parents' drinking problem. Alcohol problems in biologic relatives have also been associated with drug abuse in adopted offspring (Cadoret, Troughton, O'Gorman, & Heywood, 1986), though the importance of genetic risk for other drug abuse is less consistent. . .