Furthermore, another study has reported an association between the T/T genotype and a reduction in occipital, parietal, and temporal lobe grey matter volume in patients with schizophrenia, although the strength of this relationship is dependent upon the cumulative presence of risk alleles for the miR137 regulated genes transcription factor 4 (TCF4), prostaglandin-endoperoxide synthase 2 (PTGS2), mitogen-activated protein kinase 1 (MAPK1), and mitogen-activated protein kinase 3 (MAPK3) [71]. Here, MAPK1 is linked to schizophrenia.