P300 amplitude is related to clinical state in severely and moderately illpatients with schizophrenia

Background: Relationships between illness severity and neurobiologic abnorm alities in schizophrenia were studied in subpopulations varying in clinical severity, Methods: Auditory ERPs were collected from 28 severely ill, chronically hos pitalized schizophrenic men from a state hospital; 29 moderately ill inpati ent and outpatient schizophrenic men from a veterans hospital; and 30 healt hy male subjects from the community as controls. Clinical symptoms were eva luated in patients using the Brief Psychiatric Rating Scale (BPRS). Results: Both schizophrenic patient groups had smaller P300 amplitude than the control subjects. Severely ill patients had smaller P300s than moderate ly ill patients and scored higher on three BPRS factor scores as well as BP RS Total. Among severely ill patients, P300 amplitude was unrelated to clin ical symptoms. Among moderately ill patients, P300 was related to Withdrawa l/Retardation, Anxiety/Depression, and BPRS Total. After combining patients , Thinking Disturbance emerged as an additional correlate of P300. Group di fferences in P300 could not be accounted for by group differences in sympto m severity using analysis of covariance, Conclusions: Reduced P300 amplitude marks the diagnosis of schizophrenia, b ut also reflects individual differences in severity, including positive sym ptoms. previous failures to find relationships between positive symptoms an d P300 may have been due to a restricted range of clinical severity. (C) 19 99 Society of Biological Psychiatry.