Genetic determinants of alcohol addiction.

Animal and human studies indicate strain, species, and racial differences in biological responses to alcohol. Presumably, these are at least partly determined by genetic factors. However, until recently there has been little evidence suggesting that the condition called alcoholism is influenced by genetic factors. Although alcoholism is strongly familial (about one quarter of male relatives of alcoholics are themselves alcoholic), the condition is also associated with vocational and ethnic differences and at present there is no consistent evidence linking alcoholism to specific biochemical abnormalities. In recent years, however, an increasing body of evidence has suggested that genetic factors may play a role. These studies generally have been of two types: (1) twin and adoption studies, and (2) genetic marker studies. Two twin studies have been conducted. One indicated that monozygotic twins are more concordant for alcohol problems than are dizygotic twins. The other produced equivocal findings. Genetic marker studies have had inconsistent results. Of two adoption studies conducted, one found evidence for a hereditary factor and the other did not. It is hypothesized that severe forms of alcoholism may be heritable while milder forms have nongenetic origins. The virtues and limitations of the various studies are discussed.