The most robust association between a variant of an ADH gene and alcohol dependence is with the ADH1B*2 allele (previously known as ADH2*2). This variant is in the ADH1B gene that encodes the β2 subunit of ADH, and results in histidine instead of arginine at position 48.13 It is associated with a more rapid ethanol oxidation to acetaldehyde and is protective against alcohol dependence, with an odds ratio of 0.12 in a Chinese population.13,15 Again, this variant is common in people of East Asian descent, and rare in people of European and African descent. The protective effect of this allele seems to be weaker in European than in Asian populations.19 It is unclear how much of this variability is due to different social and environmental factors rather than unidentified coinherited genes that modify susceptibility.
