It was found that the substitution (C to T) of nucleotide 677 (rs1801133) in exon 4 of the MTHFR gene resulted in amino acid substitution (Ala222Val) and a reduction of MTHFR activity, which was most frequently studied in relation to mental disorders including SCZ12–14, autism spectrum disorders15–17, affective disorders18–20, anxiety disorders21,22 and alcohol dependence23. This evidence concerns the gene MTHFR and mental disorder.