Response of plasma beta-endorphin immunoreactivity to d-amphetamine and placebo in schizophrenic patients

The response of plasma beta-endorphin (ir) to infusions of randomly assigned d-amphetamine (20 mg) and placebo was studied in eight schizophrenic patients. Although there was no statistically significant difference between the response to d-amphetamine and placebo, significant increases in plasma beta-endorphin (ir) levels were observed following each infusion. Although heterogeneity in beta-endorphin (ir) response was observed, individual differences did not relate to clinical variables such as abnormalities on computed tomography or "process-reactive" distinctions. An excessive beta-endorphin response to placebo in schizophrenia is discussed.