To obtain their sample, the investigators first recruited alcohol-dependent patients (also called index cases or probands) who were treated in both inpatient and outpatient chemical-dependency treatment centers (including both privately and publicly funded programs). The investigators obtained the probands’ permission to contact first-degree relatives and invited those family members to participate in the study. In addition, the study included a community-based comparison group that was recruited from a variety of sources, such as dental clinics, health maintenance organizations, and a driver’s license registry. Control families with alcohol-dependent family members were not excluded from the study. This comparison group provided baseline measurements of alcohol dependence and related characteristics in the general population.
