Association between Suicidal Behavior and TPH1 and TPH2 Genes of Serotonergic System in Polish Affective Group

Suicide stayed important practical problem in psychiatry. Looking for genetic predisposition to suicide we considered polymorphisms of TPH1 and TPH2 genes, a rate limiting enzyme in serotonin synthesis. We focused on affective patients, most vulnerable to suicide psychiatric group. In the study were included 549 unrelated patients and 370 healthy controls. The selected polymorphisms were genotyped using the Taq Man single-nucleotide polymorphism (SNP) allelic discrimination method after extracting the DNA from blood sample. The Pearson’s chi-square (χ2) test and Fisher’s exact test were applied to test the genotypic and allelic associations. The results were divergent with respect to the diagnosis and suicidal behavior. TPH1 gene polymorphisms rs1800532 and rs1799913 revealed an association to diagnosis in group of male BP and MDD patients. Also rs7933505 was associated to the diagnosis of BP type I in males. TPH2 polymorphisms rs1386483 and rs4448731 turn out be associated to BP type II. There were genotypic associations to suicide attempts in four TPH1 SNPs (rs1800532, rs1799913, rs7933505, rs684302) in male group, but we found no statistically significant associations between TPH2 polymorphisms and suicidal attempts. Our results partly confirm the role of serotonergic neurotransmission in predisposition to suicide and bipolar disorder. The serotonergic system plays a great role in behavior regulation and our results support that the role may partly differ according to sex.