COMT and schizophrenia: We hypothesized that the presence of the G allele of the COMT rs4680 or rs4818 polymorphism, both related to higher COMT activity and reduced dopaminergic function, will be associated with pronounced cognitive decline and more severe clinical symptoms in schizophrenia, compared to presence of the A or C allele of the COMT rs4680 or rs4818 polymorphisms, respectively.