Families were obtained by recruiting alcohol-dependent probands (i.e., index cases) who were in treatment and who gave permission to contact their family members. This approach generated a dataset of 1,857 families consisting of 16,062 individuals as of March 2010. Moreover, the researchers identified a genetically informative subset comprising 262 families with at least three first-degree relatives who met lifetime criteria for both Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised (DSM–III–R) (American Psychiatric Association 1987) alcohol dependence and Feighner definite alcoholism;4 this subset became the focus of genetic analyses. The extensive characterization of subjects also allowed analysis of the role of hereditary characteristics (i.e., endophenotypes) that often are associated with alcoholism but are not direct symptoms of alcoholism, such as certain electrophysiological traits, drug dependence, other related psychiatric conditions, and personality measures (Edenberg 2002).
