Association of 677C>T polymorphism of methylenetetrahydrofolate reductase (MTHFR) gene with bipolar disorder and schizophrenia

Methylenetetrahydrofolate reductase (MTHFR) gene polymorphism 677C>T has been shown to be a risk factor for psychiatric disorders. We investigated the genotype and allelic frequencies of MTHFR 677C>T polymorphism in the group of patients with bipolar disorder type I (BDI) (n = 200) and schizophrenia (n = 200), and in the control group (n = 300). Odds ratio (OR) for patients with BD and schizophrenia with 677T allele was 1.988 ((95% CI = 1.370-2.883); P = 0.0003 (P = 0.0006 after Bonferroni correction)) and 1.796 ((95% CI = 1.237-2.609); P = 0.0020 (P = 0.0040 after Bonferroni correction)), respectively. The stratification of patients based on gender revealed significant association of 677T allele with male patients with BDI and schizophrenia (OR = 2.393; 95% CI = 1.429-4.006; P = 0.0008 and OR = 2.036; 95% CI = 1.207-3.433; P = 0.0073, respectively). This finding indicates possible association of BD and schizophrenia with the 1p36.3 MTHFR locus.