with the case for polymorphisms affecting acetaldehyde levels via ADH genes, the aversive reaction to alcohol resulting from the ALDH2-2 allele has been robustly demonstrated to result in a substantial protective effect against alcoholism in a number of studies (e.g., Chen et al., 1999, Luczak et al., 2006; Thomasson et al., 1991). In behavioral terms, these individuals experience unpleasant effects of alcohol upon consumption, which makes them less likely to consume alcohol and sharply decreases their risk for developing an AUD. Importantly, the narrowly-defined phenotype of unpleasant subjective responses to alcohol (i.e., “flushing” response) has helped scientists further understand the neurobiology of alcohol and its effects, as well as genetic factors underlying this posited protective behavioral phenotype.
