We genotyped 15 tagging-single nucleotide polymorphisms (SNPs) including 4 SNPs, which were previously reported to be associated with suicidal behavior, using the TaqMan probe assays and the polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) method.
We found no significant differences in genotypic distributions (uncorrected p = 0.06–0.98) or allelic frequencies (uncorrected p = 0.09–0.95) of the fifteen SNPs between the completed suicides and control groups. Haplotypes constructed with these SNPs were also not associated with suicide (uncorrected p = 0.03–0.96 and corrected p = 0.20–1.00). Even when we took sex and suicidal methods (violent or non-violent) into account for the analyses, no significant differences in genotypic distributions, allelic/haplotypic frequencies were found in the two groups.
Our results suggest that the common SNPs and haplotypes of the TPH2 gene are unlikely to contribute to the genetic susceptibility to suicidal behavior in Japanese population.