Alcohol dependence was one of the first behavioral disorders shown to have validated genetic contributions. Polymorphisms in the alcohol metabolizing enzymes are the most strongly associated genetic variants that influence alcohol consumption and alcohol dependence. In 1972, individuals of Asian descent were reported to have facial flushing and decreased tolerance when exposed to alcohol (Wolff, 1972). The flushing reaction after ingesting alcohol is secondary to a deficiency of aldehyde dehydrogenase (specifically ALDH2), an enzyme involved in the metabolism of ethanol (Goedde et al., 1980). The ALDH2 deficiency was found to be present in a large part of the general Japanese population, but uncommon in alcohol dependent individuals, implying a protective role for the deficiency of ALDH2 in alcohol dependence (Harada et al., 1982).
