was formed in 1989 to map and characterize the genetic variants associated with alcoholism (Bierut et al., 2002). COGA is a family-based genetic study with nine research sites throughout the U.S. Nuclear and multigenerational families were ascertained through a proband in treatment for alcohol dependence. The initial sample consisted of 105 families with 987 individuals. Results from the first genome-wide scan provided evidence of linkage for loci on chromosomes 1 and 7 and suggestive linkage on chromosome 2 with alcohol dependence; linkage on chromosome 2, conferring protection against alcohol dependence, near the alcohol dehydrogenase genes was also found (Reich et al., 1998). A follow up study in 157 independent families densely affected with alcoholism was conducted and provided further evidence of linkage to chromosomes 1 and 7 with new loci identified on chromosomes 2 and 3 (Foroud et al., 2000).
