Polymorphisms of the D2 dopamine receptor gene and alcoholism and other substance use disorders.

The A1 (minor) allele of the D2 dopamine receptor (DRD2) gene has been shown to be associated with alcoholism, particularly the severe form of this disorder. This allele has also been found to be involved in a variety of other substance use disorders including, cocaine and nicotine dependence, polysubstance abuse and obesity. Moreover, reduced dopaminergic function has been found in subjects carrying the DRD2 A1 allele, suggesting that the DRD2 may be a reinforcement or reward gene. Analysis of the available data suggests that the DRD2 variants represent one of the most prominent single-gene determinants of susceptibility to severe alcoholism and other substance use disorders. However, environmental factors and other genes must, in combination, play the larger role.