The first whole autosomal genome scan for genetic linkage to alcohol dependence was conducted in the Southwest American Indian population. In that study highly suggestive evidence for linkage, expressed as the log of the odds (LOD score) of a locus being linked to the phenotype rather than unlinked, emerged for two genomic regions. The best evidence was seen on chromosome 11p15.5 (LOD score: 3.1) near the D4 dopamine receptor (DRD4) and tyrosine hydroxlyase (TH) genes, with secondary evidence on chromosome 4p11-p13 near the alpha 2 and beta 1 GABA receptor genes (GABRA2 and GABRB1, respectively) and 4q23-q25 near the alcohol dehydrogenase gene cluster [18]. Evidence for linkage has also been demonstrated for three alcohol dependence phenotypes in California Indians. The strongest result was reported for chromosome 5q21.2-q21.3 in a study of an alcohol craving phenotype (LOD score 4.5) [16]. Chromosomes 4q22.1 and 12q24.32 yielded LOD scores exceeding 2 for an alcohol use severity phenotype, and chromosomes 6p21.1, 15q22.2-q25.3, and 16p13.3 yielded LOD scores that exceeded 2 for a withdrawal phenotype [20]. The evidence for linkage to chromosomes 4, 15, and
