An electrophysiological study on the effects of tryptophan and cortisol on schizophrenic and other mentally ill patient groups and on normal subjects.

Direct current potentials measured on the scalp suprajacent to the midline prefrontal cortex appear to monitor the metabolic activity, via CO2 production, of this portion of the cerebrum. Changes in the frontal potential 90 min after oral administration of 2.0 g L-tryptophan and of 50 mg cortisol were studied in groups of subjects defined by age, sex, psychiatric diagnosis, and medication. Twelve normal males, 10 nonschizophrenic male psychiatric inpatients, and 6 normal females showed a significant decrease in their frontal voltages, most marked in the females, after tryptophan loading. A nonsignificant voltage increase was produced by subsequent administration of cortisol. Tryptophan-loading had an opposite, voltage-increasing effect, on the 30 schizophrenic subjects tested. This abnormal response was greatest in the male and postmenopausal schizophrenic subjects. Besides this sex effect, the abnormality increased with age up to a point, and was decreased by antipsychotic medication and cortisol. An explanation in terms of an abnormality in the relative hydroxylation of indoles in schizophrenic subjects is proposed.