The Collaborative Study on the Genetics of Alcoholism (COGA) is a family study of alcohol dependence which includes 6 subject recruitment centers across the United States (Farmington, CT; Brooklyn, NY; Indianapolis; IN, St. Louis, MO; Iowa City, IA; and San Diego, CA). Probands were recruited from treatment settings and were required to meet criteria for DSM-III-R (American Psychiatric Association, 1987) alcohol dependence and Feighner definite alcoholism (Feighner et al., 1972). Probands were also required to have at least two first-degree relatives living in one of the COGA catchment areas who were available for the study. All first-degree relatives of probands were sought for interview during the initial phase of the study. Siblings of probands are the focus of the current study. The institutional review board at each site approved the protocol, and written informed consent was obtained from all subjects. Additional details about the study have been published elsewhere (Bucholz et al., 1996; Culverhouse et al., 2005; Nurnberger et al., 2004; Reich, 1996; Schuckit et al., 1998).
