after alcohol consumption and is protective against alcohol dependence (103) (Figure 2). A meta-analysis of the ADH1B*2 allele in Han Chinese and Japanese showed that individuals who are homozygous for this variant (His48/His48) have a fivefold decrease in risk for alcohol dependence compared with individuals who are heterozygous for this variant (Arg48/His48) (142). In Europeans, the risk for developing alcohol dependence is twofold lower in His48/His48 carriers compared with Arg48/His48 carriers (142). Recently, a case-control study in populations of European and African ancestry demonstrated that the ADH1B*2 (His48) allele in these populations is associated with a lower maximum number of drinks in a 24-h period (p = 3 × 10−13) and has a strong protective effect on DSM-IV alcohol dependence in both populations (odds ratio = 0.34, p = 6.6 × 10−10) (16). The protective effect of ADH1B*2 was not detectable by a GWAS approach in studies involving populations of European or African descent because none of the variants on these genotyping chips showed high linkage disequilibrium with this rare variant. These studies demonstrate that the ADH1B*2 allele correlates with reduced alcohol consumption and risk for alcohol dependence in all populations, though the allele frequencies vary in people of different
