MTHFR and psychiatric disorder: 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.