Abstract
Serotonin plays an important role in mood regulation, but the involvement of serotonin pathway genes in the development of bipolar I disorder (BP-I), a mood disorder, is not clear. We selected 21 single-nucleotide polymorphisms (SNPs) within the HTR2A gene, 8 within the SLC6A4 gene and 23 within the TPH2 gene for genotyping using the GoldenGate genotyping assay. A total of 375 patients with BP-I and 475 normal controls were recruited. Two out of 21 SNPs (rs1475196 and rs9567747) in the HTR2A gene and 1/23 SNPs (rs17110566) in the TPH2 gene were significantly associated with BP-I, both genotype-wise and allele-wise. Furthermore, a specific haplotype in the HTR2A gene showed a significant association with BP-I. Our results indicate that the HTR2A and TPH2 genes in the serotonin pathway play important roles in susceptibility to BP-I.