A third hypothesis is that the association of early alcohol use with alcoholism risk arises because early use of alcohol in adolescence and alcoholism in adulthood are manifestations of a general inherited liability to disinhibitory psychopathology.24,25 Support for this idea came initially from a study of nearly 9000 twins that showed that early use of alcohol was heritable and that its association with alcoholism risk was mediated entirely by genetic factors.19 This model also predicts that early use of alcohol should be a nonspecific risk factor for a wide range of behavioral pathologies because it is an indicator of a general disposition toward disinhibited behavior. Consistent with this expectation, alcohol use before 15 years of age is associated with attention deficit/hyperactivity disorder, conduct disorder, personality measures of impulsivity, psychophysiological indicators of disinhibition, academic underachievement, and abuse of substances other than alcohol.18 In their 2008 review of these mechanisms, McGue and Iacono26 point out that none of these mechanisms are mutually exclusive, and that early use of alcohol may be an indicator of inherited risk and disrupt the course of adolescent development.
