D2 dopamine receptor gene is associated but not linked with alcoholism

Article Abstract:

A study by Blum et al. in the May 1990 issue of The Journal of the American Medical Association reported that the prevalence of a variant of the gene for the D2 dopamine receptor, the A1 allele, was significantly greater among alcoholics than among nonalcoholics. This finding ignited much controversy and skepticism, and studies since that time have produced conflicting results. One problem with all of these studies has been a small sample size. In the October 2, 1991 issue of The Journal of the American Medical Association, two more studies on this issue are reported. The study by Comings et al. reported findings from several large populations, that the A1 allele was more prevalent among alcoholics than normal subjects. However, the prevalence rate was less than 50 percent in alcoholics and they concluded that the presence of this allele was not a cause of alcoholism, but rather a modifier of the expression of alcoholism. In the study by Gelernter et al., no significant difference was found in the prevalence of the A1 allele between alcoholics and nonalcoholics. When results from the six studies on this issue are combined, the prevalence of the A1 allele in alcoholics is seen to be certainly higher than that in control subjects. It would thus appear that the A1 allele contributes to alcoholic behavior, but does not cause it. This is the first instance that a genetic link to a common psychiatric disorder has been discovered. Further studies with larger populations are needed to find the exact prevalence of the allele and the clinical use of such knowledge. (Consumer Summary produced by Reliance Medical Information, Inc.)

Diagnosis, Mental illness, Mental disorders, Genetic disorders, editorial

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The A1 allele at the D2 dopamine receptor gene and alcoholism: a reappraisal

Article Abstract:

Accumulated evidence on the relation between the A1 allele at the D2 dopamine receptor (DRD2) gene and alcoholism remains inconclusive. A 1990 study found that carriers of the A1 allele at DRD2 had a significant risk of alcoholism. Since then, several studies on the A1 allele at DRD2 have been conducted, some of which support an association with alcoholism and some of which refute it. In a review of data from all studies on the A1 allele at DRD2 and alcoholism, there was no significant difference in the frequency of A1 between alcoholics and non-alcoholics. Furthermore, heterogeneity was greater within the groups of alcoholics and non-alcoholics than between the groups. Frequency of the A1 allele varies among different ethnic groups. All studies that limited participants - alcoholics and non-alcoholics - to one ethnic group found no differences in A1 frequency between the two groups. These findings suggest that heterogeneity within the groups and ethnicity may explain the association between the A1 allele and alcoholism found in some studies.

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