Aims: The frequency of the Taq I A alleles (A1 and A2) of the D2 dopamine receptor (DRD2) gene was examined in Caucasian post-traumatic stress disorder (PTSD) patients and controls.
Results: In 91 PTSD patients, the frequency of the A1 allele was higher (P = 6.12 x 10(-3)) than in the 51 controls. In the 38 PTSD harmful drinkers (>or=60 g alcohol/day), A1 allelic frequency was higher (P = 3.91 x 10(-2)) than in the 53 non-harmful drinkers (<60 g alcohol/day), the former being also higher (P = 3.76 x 10(-4)) than in controls. However, there was no difference between non-harmful drinkers and controls. Based on DRD2 allelic association, the 35 PTSD patients with the A1(+) (A1A1, A1A2) allele consumed more than twice the daily amount of alcohol than the 56 patients with the A1(-) (A2A2) allele (P = 1.94 x 10(-3)). When the hourly rate of alcohol consumed was compared, A1(+) allelic patients consumed twice the rate of the A1(-) allelic patients (P < 10(-7)).
Conclusion: The DRD2 A1 allele was associated with PTSD. However, this association was found only in the harmful drinkers. PTSD patients with the A1(+) allele consumed more alcohol than patients with the A1(-) allele. The importance of determining alcohol consumption in DRD2 association studies with PTSD is suggested.