The distribution of ADH1B and ALDH2 coding variants differs greatly among different populations; for both genes, the protective alleles most commonly are found in people of East Asian origin (for more information, see the article by Eng et al. in this issue). Variations in genes encoding other ADH enzymes influence alcoholism risk in other populations. For example, ADH4 variants strongly affect alcoholism risk in populations of European descent (Edenberg et al. 2006). Furthermore, noncoding variations in various alcohol-metabolizing enzymes likely also affect risk for alcoholism (Edenberg et al. 2006). These noncoding variants should be studied in more populations.
