the ADH1 enzyme, ADH1B*1, by further decreasing the odds ratio of alcohol dependence to 0.05 in the presence of both alleles.15 The protective effect of the ALDH2*2 allele is susceptible to environmental pressures. A study by Higuchi and colleagues18 found that the fraction of Japanese alcoholics carrying the ALDH2*2 allele increased from 3% in 1979 to 13% in 1992. This increase is believed to be due to an overall increase in alcohol consumption in Japanese society during that period.
