COMT and schizophrenia: The role of COMT in schizophrenia has been extensively studied, yet results have unequivocally shown that neither genetic variants nor the catalytic activity of the enzyme have great intrinsic influence on schizophrenia risk (Chen et al., 1996; Daniels et al., 1996; Riley et al., 1996; Wei et al., 1996; Karayiorgou et al., 1998; Wei and Hemmings, 1999; De Chaldee et al., 2001; Semwal et al., 2001; Strous et al., 2006).