The COGA investigators also defined a phenotype termed “unaffected,” which was assigned to people who used alcohol but did not meet the criteria for alcohol dependence (Reich et al. 1998).4 Analysis of people with the “unaffected” phenotype, who were relatively rare in the COGA families, is interesting because these people developed few or no alcohol-related problems despite living in a family environment characterized by the presence of several alcoholic family members and, consequently, excessive alcohol consumption. This suggests that these people may carry genetic factors that help protect against the development of alcoholism.
