COGA is a large-scale multi-center family study with 10 collaborative sites across the United States. The sample consists of families containing probands meeting both DSM-IIIR and Feighner criteria for AD ascertained since 1989 from outpatient and inpatient alcohol treatment centers at six sites across the United States: Indiana University, State University of New York Health Science Center, University of Connecticut, University of Iowa, University of California/San Diego and Washington University in St Louis. Families were interviewed using a poly-diagnostic instrument, the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA), which assesses Feighner, DSM-IIIR, DSM-IV, and ICD-10 criteria for major psychiatric disorders. More than 1300 probands with AD have been recruited. Unaffected subjects were defined as individuals who drank but did not meet criteria for AD or illicit substance dependence. A subset of the COGA sample was identified as a group of high-density families with 3 or more first-degree relatives who met lifetime criteria for AD. The institutional review boards from all of the participating institutions approved the study (Edenberg et al., 2008; Wang et al., 2009).
