MTHFR and schizophrenia: As seen in Table 3, these pilot results show that schizophrenia patients had significantly lower (50%) levels of 5-MTHF (11.70 nM; n = 34) than those observed in healthy controls (22.67 nM; n = 42), and there was a significant difference in the frequency of MTHFR genotype variations, but not PON1 genotype variations, between the recruited schizophrenia patients and healthy controls.