Association Study of TPH1 (rs1800532) and TPH2 (rs4570625) Polymorphisms in Type 1 Bipolar Disorder in Iran

Bipolar disorder (BD) has episodes of depression and mania or hypomania. Several studies have been conducted on the role of genes in bipolar disorders and suicidal behaviors, and serotonin-associated genes, Tryptophan hydroxylase (TPH1 and TPH2), are proposed as one of the main effective genetic factors. In this study, 116 BD patients and 118 age and gender-matched healthy subjects were recruited as the control group. The polymorphisms of THP1 (rs1800532) and TPH2 (rs4570625) genes were identified using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. There was a positive association of bipolar disorder with CC genotype (P = 0.04) for TPH1 A218C polymorphism, yet not for other genotypes and alleles. There was no association for the genotype and allelic frequency distributions of TPH2-703G/T between bipolar patients and healthy control groups. The TPH1 and TPH2 gene polymorphisms are subjects of many researches. There are contradictions in investigations around the world. These results are in agreement with studies of other populations, yet are different from many studies. There is a need for further investigations.