The methylenetetrahydrofolate reductase (MTHFR) gene variant C677T, involved in the one-carbon metabolic pathway which is essential for DNA biosynthesis and the epigenetic process of DNA methylation, a cardiovascular and ischemic stroke independent risk factor, has been associated with schizophrenia, bipolar and unipolar depressive disorder (Peerbooms et al., 2011; El-Hadidy et al., 2014). The gene discussed is MTHFR; the disease is schizophrenia.