No association between MTHFR C677T polymorphism and completed suicide

MTHFR C677T polymorphism (rs1801133) was associated with numerous psychiatric conditions but no prior study investigated whether it predisposes to completed suicide. We typed rs1801133 in 692 suicide victims and 3257 controls representative of a Polish adult population (the WOBASZ cohort). Although we had a power of 0.8 to detect (at alpha 0.05) an allelic OR=1.19, we did not find significant difference among suicides vs. controls in the prevalence of the MTHFR 677T allele (OR=1.02, p=0.759) or the TT genotype (OR=1.01, p=0.926). Since among controls we found an association between TT and depression defined by Beck Depression Inventory (BDI, OR=1.61, p=0.049) we also compared suicides with controls without signs of depression (BDI≤11) but found no association (OR=1.0, p=0.976). Analyses within suicides showed trends (not significant after Bonferroni correction) for correlations between the dose of the T allele and age at death among males and blood ethanol concentration among females, who committed suicide under the influence of alcohol. We conclude that MTHFR C677T polymorphism is not a risk factor for completed suicide. The sex-specific trends for correlations between rs1801133 and age at death, and blood ethanol concentration should be studied further. ► MTHFR rs1801133 influencing folate metabolism predisposes to psychiatric diseases. ► We tested for the association of rs1801133 with completed suicide and found none. ► Among suicides we found sex specific trends for genotype–phenotype correlation. ► Among controls there was an association between rs1801133 and depression.