Auditory evoked potentials as possible predictors of outcome in schizophrenic outpatients

As part of a follow-up study on long-term neuroleptic treatment, 36 schizophrenic out-patients under neuroleptic treatment were studied in an 'auditory oddball' event-related potential paradigm after a 3-month stabilization phase following clinical discharge. In the first cross-sectional analysis, we evaluated the influences of age and gender and tried to find auditory evoked potential (AEP) variables, which might be promising as potential predictors of the course of illness. Compared with healthy age-matched controls, the patients showed smaller N1/P3-amplitudes. Males and females showed only minor AEP-differences, the amplitude N1/P2 being slightly higher in females. Age correlated positively with the latency P3 and negatively with the latency P2R. The interpeak latency P3-P2R showed the highest correlation with age. Test/re-test reliability was measured and variables with r less than 0.60 were rejected. The amplitudes N1/P2 and N1/P3 showed the highest test/re-test correlations. The more severely disturbed patients (global assessment scale [GAS]-score less than 65) had shorter interpeak latencies P2F-N1F than the less disturbed patients (GAS greater than or equal to 65). Patients with a high rate of relapse tended to have shorter interpeak latencies P2F-N1F than patients with low rates of relapse. Our results indicate that the interpeak latency P2F-N1F has an acceptable test/re-test reliability (C3: r = 0.72; C4: r = 0.80) and is related to clinical variables characterizing the course and outcome of illness. This leads to the hypothesis that a short interpeak latency, P2F-N1F, might be a predictor of poor prognosis.