Probands were recruited from consecutive admissions to inpatient, outpatient, and aftercare alcohol or drug treatment settings within 6 catchment areas in the United States: Brooklyn, New York; Indianapolis, Indiana; Iowa City, Iowa; San Diego, California; Farmington, Connecticut; and St. Louis, Missouri (41). Probands were required to meet criteria for DSM-III-R alcohol dependence (42) and Feighner definite alcoholism (43), and to have at least 2 first-degree relatives available for study in the catchment area; all first-degree relatives were sought for baseline and follow-up interviews 5 years later (19, 44). The COGA protocol was approved by the institutional review board at each research site and all subjects provided written informed consent.
