Dopamine D2 Receptor Gene Polymorphisms Are Associated with Suicide Attempt in the Japanese Population

Background: Some reports have suggested the involvement of the D2 dopaminergic function in the expression of suicidal behavior. Here, we examined associations between suicide attempts and two kinds of functional polymorphisms in the dopamine D2 receptor (DRD2) gene, namely, TaqIA and –141C Ins/Del. Methods: Subjects included 120 suicide attempters and 123 unrelated volunteers. Those who attempted suicide were severely injured and were transferred to the emergency unit in our university hospital. To determine each genotype, we performed polymerase chain reaction and restriction fragment length polymorphism analyses. Results: We found significant differences in genotypic and allelic frequencies of –141C Ins/Del and TaqIA polymorphisms between suicide attempters and healthy controls (–141C Ins/Del, p = 0.01; TaqIA,p = 0.036). The Ins allele of –141C Ins/Del was significantly more frequent in suicide attempters (p = 0.011), as well as the A2 allele of TaqIA (p = 0.017). Haplotype analysis revealed no significant linkage disequilibrium between –141C Ins/Del and TaqIA polymorphisms (D′ = 0.226, r2 = 0.016, p = 0.10). Conclusions: These findings suggest that DRD2 gene polymorphisms may be involved in the biological susceptibility to suicide.