Abstract: Objective To explore the association of single nucleotide polymorphism(SNP) analysis of a novel tryptophan hydroxylase isoform(TPH2) gene G1463A with depression and suicidal behavior.Methods We collected the specimens of peripheral blood from 300 depression patients and 292 controls in a population of northern China and extracted their genomic DNA.TPH2 gene G1463A was detected with TaqMan SNP genotyping assay and the association of polymorphisms of TPH2 gene with depression and suicidal behavior was analyzed using SPSS 17.0.Results The genotypic frequencies of the SNPs did not deviate from Hardy-Weinberg equilibrium in both case and control groups(P>0.05).Compared with the control group,significant differences of genotypes and alleles of TPH2 gene G1463A SNP were observed in patient group(38.0% vs 50.0% for A/A,0.3% vs 40.1% for T/T,61.7% vs 9.9% for A/T,68.8% vs 55.0% for allele A,and 31.2% vs 45.0% for allele T;P<0.05 for all).The genotypes of TPH2 gene G1463A in patient group were significantly associated with Hamilton Depression Rating Scale(HAMD) total score and factors(P=0.000).There were no significant associations of genotypes and alleles of TPH2 gene G1463A with suicide behavior in patient group(P>0.05).Conclusion TPH2 gene G1463A SNP significantly associates with unipolar depression,but may not associate with the susceptibility of suicidal behavior in depression patients.