Residual symptoms and P300 in schizophrenic outpatients.

A reduced P300 amplitude has often been found to be related to schizophrenic psychopathology. It is still unclear, however, whether this relationship is trait- or state-dependent. We investigated 88 stabilized schizophrenic outpatients during a 2-year follow-up period. Multivariate analyses revealed that patients who had reduced P300 amplitudes showed pronounced residual symptoms, especially thought disorder (Brief Psychiatric Rating Scale). Intraindividual changes in that psychopathology were not correlated to corresponding changes of the P300 amplitude, so the relationship between schizophrenic psychopathology and P300 amplitude appears to be, at least in part, trait-dependent. A reduced P300 amplitude may characterize a subgroup of schizophrenic patients with a disposition to cognitive disturbances and incomplete remissions.