Dopamine D1 receptor gene polymorphism is associated with prophylactic lithium response in bipolar disorder.

Previously, we have found an association between the -48 A/G polymorphism of the dopamine receptor D1 (DRD1) gene and bipolar disorder. The aim of the present study was to investigate a possible association of this polymorphism with the quality of the prophylactic lithium response in bipolar patients. Ninety-two patients (39 male, 53 female), aged 30-77 (mean: 54 years) were studied. They have received lithium for prophylactic purposes for 5-27 years (mean: 15 years). Twenty-four patients were identified as excellent lithium responders (ER), 48 patients as partial responders (PR), and 20 patients were non-responders (NR). They all were genotyped for -48 A/G polymorphism of the DRD1 gene. The frequency of G/G genotype in ER, PR, and NR patients was 21%, 48%, and 60%, respectively, and the frequency of G allele was 58%, 76%, and 80%, respectively. The results obtained suggest that the higher frequency of G allele, and G/G genotype, which has been associated with a predisposition to bipolar illness, is also connected with a poorer prophylactic effect of lithium.