COMT and schizophrenia: MAOA mRNA was significantly increased by 45% in the substantia nigra in schizophrenia cases compared with controls (F=6.34, df=56, P=0.015), but no diagnostic changes were found in the levels of MAOB mRNA (F=0.81, df=53, P=0.372) or COMT mRNA (U=462, z=0.89, P=0.371; Figures 2f–h, respectively).