The TaqI A DRD2 polymorphism in type II alcohol dependence: a marker of age at onset or of a familial disease?

Cloningerʹs type II is a severe, early-onset, male-limited, and genetically influenced, impulsive form of alcoholism. Significant association has been reported between the A1 allele of the D2 dopamine receptor (DRD2) gene, substance misuse and personality traits of impulsivity and novelty seeking. We assessed the association between the TaqI A DRD2 gene polymorphism with Cloningerʹs typology and family history of alcohol abuse, which is thought to be more frequent in type II alcoholics. Fifty-one male alcohol-dependent patients were discriminated between type I and type II according to age at onset of alcohol-related problems and interviewed about family history of alcoholism. The associations between DRD2 (A1 or A2 alleles), family history, and typology were assessed by Pearsonʹs chi-square test. Although typology was not associated with the studied polymorphism, a higher rate of general family history of alcohol abuse was still observed in type II patients (χ21 = 4.53; P = .033). Furthermore, the A1 allele of the DRD2 was significantly associated with paternal history of alcoholism (χ21 = 4.66; P = .031) and male, first-degree, collateral history of alcoholism (χ21 = 4.40; P = .036). Age at onset of alcohol-related problems as main discriminator between type I and type II alcohol dependence does not seem to be associated by the TaqI A DRD2 polymorphism. However, the A1 allele of the DRD2 may be a marker of male familial alcoholism, which has been associated with type II alcohol dependence.