Electroencephalographic findings in relation to diagnostic constructs in psychiatry

A group of 759 patients with final DSM-I and -II diagnoses of schizophrenia was identified among a cohort of 1494 adults who were hospitalized between 1965 and 1972. Admission EEG recordings were done in each patient during waking, activation procedures, drowsiness, and sleep. All cases were reclassified according to the Feighner et al. criteria, and relationships between the EEG, reassigned diagnosis, and outcome were examined. One-third of the schizophrenics were rediagnosed as having affective, organic, or other disorders. EEG abnormalities predicted diagnostic change and relatively favorable prognosis. Mean alpha frequencies were slower in schizophrenics than in patients with other DSM I-II disorders, and less in patients with Feighner et al. diagnoses of schizophrenia than in some rediagnosed categories. In 1980-82, matched samples from the original cohort with affective, schizophrenic, and mixed Feighner et al. diagnoses were followed and evaluated blindly with the SADS-L. RDC follow-up diagnoses were significantly correlated with the index EEG findings in terms of higher alpha average frequencies proportional to the amount of affective psychopathology. A subgroup of high functioning individuals within the RDC schizophrenic category was identified with affective symptomatology early in the course of illness, normal EEGs, and high alpha average frequencies. Patients with a consistent diagnosis of schizophrenia according to the three nosologic systems were shown to function better in some areas if the index EEG was abnormal. Discriminant function analysis established that DSM-I and -II categories possessed the greatest long-term predictive accuracy which was enhanced by the EEG diagnosis and alpha average to a level of more than 50%. The Feighner et al. and RDC diagnostic systems were not as relevant for prediction of long-term follow-up status.