MTHFR and schizophrenia: We investigated whether antipsychotic treatment response was influenced by the C677T and A1298C polymorphisms of methylenetetrahydrofolate reductase (MTHFR), and A66G of methyltetrahydrofolate-homocysteine methyltransferase reductase (MTRR)-genes central to folate and homocysteine metabolism and methylation, pathways often altered in schizophrenia patients.