Most published genome-wide association studies (GWAS) of addictions have focused on smoking behavior or AD. Four GWAS of AD with a range of 1,100 to 1,897 patients have been published thus far, and only two SNPs have received modest support of replication in a subsequent study(92). One GWAS(93) has identified nine SNPs located in genes, for example, the CDH13 and ADH1C genes, to be nominally associated with AD, including rs1614972 on the ADH1C gene (P = 0.0001). Another study (94) reported that fifteen SNPs yielded P < 10−5, but in two independent replication series, no SNP passed a replication threshold of 0.05. Edenberg et al.(95) found that 15 SNPs in the ADH gene cluster were nominally significant. However, no single SNP met genome-wide significance. Other studies(96, 97) also failed to report genome-wide significance in the ADH gene cluster. Another study(98) compared six published association studies between AD and the seven ADH genes and only a few SNPs reached the P value < 0.001 across this region.
