Origins and Consequences of Age at First Drink. I. Associations With Substance-Use Disorders, Disinhibitory Behavior and Psychopathology, and P3 Amplitude Matt McGue, William G. Iacono, Lisa N. Legrand, Steve Malone, and Irene Elkins Background: Although an early age at first drink has been repeatedly associated with substantially elevated rates of alcoholism, the mechanisms underlying this association remain unclear. We investigated whether the association of age at first drink (AFD) with alcoholism was more consistent with the hypothesis that the former causes the latter or the hypothesis that both are manifestations of some common vulnerability. Methods: We investigated whether substance use and mental health disorders, education, IQ, and personality were associated with AFD in a sample of 2670 adults; whether P3 amplitude was associated with AFD in a sample of 1127 17 year olds; and whether indicators of disinhibitory psychopathology assessed at age 11 predicted AFD by age 14 in a sample of 1343 adolescents. Results: In adults, AFD was associated not only with alcohol dependence, but also with a broad array of indicators of disinhibitory behavior and psychopathology including nicotine dependence, illicit drug abuse and dependence, conduct disorder, antisocial personality disorder, underachievement in school, and the personality trait of constraint. In 17 year olds, AFD was also associated with reduced P3 amplitude, a well-documented psychophysiological marker of alcoholism risk. Finally, in the early-adolescence sample, measures of behavioral disinhibition, including oppositionality, hyperactivity/impulsivity, and inattentive- ness assessed at age 11 predicted drinking onset by age 14. Conclusions: Our findings indicated that AFD is not specifically associated with alcoholism but rather is correlated with a broad range of indicators of disinhibited behavior and psychopathology. Moreover, individuals who first drink at a relatively early age manifest elevated rates of disinhibitory behavior and psychopathology before they first try alcohol. Taken together, these findings suggest that the association of AFD with alcoholism reflects, at least in part, a common underlying vulnerability to disinhibitory behavior. Whether an early AFD directly influences risk of adult alcoholism remains unclear. Key Words: Age at First Drink, Alcoholism, Disinhibitory Behavior, Disinhibitory Psychopathology. I N 1997 GRANT and Dawson published an influential analysis of the National Longitudinal Alcohol Epidemi- ologic Survey in which they reported a striking association between age at first drink (AFD)* and rate of alcoholism (Grant and Dawson, 1997). In a sample of more than 27,000 ever-drinking adults, the rate of lifetime alcohol dependence (AD) was four times higher among those who started to drink by age 14 years compared with those who had not started to drink until age 20 years or older (lifetime rates of 40 vs. 10%). Not only has Grant and Dawson’s finding been replicated in subsequent research (Dewit et al., 2000), but AFD has also been associated with a range of other negative life outcomes, including increased likelihood of heavy drinking (Muthén and Muthén, 2000), abuse of tobacco and other illicit substances (Schuckit and Russell, 1983), low scholastic achievement (Hawkins et al., 1997), and psychiatric problems (Schuckit and Russell, 1983). Although the association between AFD and alcoholism seems to be robust and replicable, the causal mechanisms that underlie this association remain obscure. One expla- nation favored by several investigators is that an early AFD, perhaps by interfering with normal developmental pro- cesses, exerts a relatively direct causal influence on alco- holism risk (Dewit et al., 2000; York, 1999). In this case, prevention efforts aimed at delaying the AFD might be expected to effect subsequent reductions in the rate of From the Department of Psychology, University of Minnesota, Minneap- olis, Minnesota. Received for publication September 26, 2000; accepted May 8, 2001. Supported in part by USPHS Grants AA00175, AA09367, and DA05147. Reprint requests: Matt McGue, PhD, Department of Psychology, University of Minnesota, 75 East River Rd., Minneapolis, MN 55455; Fax: 612-626- 2079; E-mail: mmcgue@tfs.psych.umn.edu Copyright © 2001 by the Research Society on Alcoholism. *Throughout the paper we use the term “age at first drink” rather than “age at drinking onset” because most studies, as well as ours, assess the age at which respondents first tried alcohol rather than the age at which they first established a regular pattern of drinking. Although correlated, the two ages are likely to differ markedly, at least for some adolescents. 0145-6008/01/2508-1156$03.00/0 ALCOHOLISM:CLINICAL AND EXPERIMENTAL RESEARCH Vol. 25, No. 8 August 2001 1156 Alcohol Clin Exp Res, Vol 25, No 8, 2001: pp 1156–1165