For alcoholism, as for other disorders, one can best establish the importance of environmental risk factors and their interaction with genetic effects using prospective study designs. Psychiatric disorders, such as alcohol dependence, typically have an early onset, however (e.g., Nelson et al. 1996); therefore, prospective studies beginning in adulthood still would be largely retrospective with respect to risk factors for such disorders. For example, in the National Comorbidity Survey, a large psychiatric epidemiological survey, the median age-of-onset of alcohol dependence symptoms was around age 20. Important psychiatric predictors of increased risk of alcohol dependence, such as childhood conduct disorder, are of even earlier onset (Kessler et al. 1997a). Prospective studies of risk factors for alcohol dependence would therefore be initially pediatric studies. Such childhood studies have the advantage that they typically allow assessment of both the parent and the offspring generation as well as of multiple siblings from the same family, making this research both feasible and cost-effective.8 In the future, it seems likely that such prospective family studies will provide the basis for a better understanding of the genetic effects and GxE interaction effects on alcohol dependence and associated psychiatric disorders.
