Several considerations strongly suggest that GxE interaction effects may be important in the development of alcohol dependence. For example, surveys that have assessed lifetime prevalence of various psychiatric disorders have noted that alcohol dependence and disorders such as depression, anxiety disorders, and history of childhood behavior problems (i.e., conduct disorder) occur together (i.e., are comorbid) much more frequently than would be expected by chance (Regier et al. 1990; Kessler et al. 1997a). Interpretations of such comorbidity have typically emphasized processes occurring within the person. For example, depression may be a risk factor for or a consequence of alcohol dependence; alternatively, both disorders may be influenced by common risk factors in the person.
