Dexamethasone suppression test in positive and negative schizophrenia.

Fifty-four inpatients with a DSM-III diagnosis of schizophrenia were studied. Patients were divided into positive and negative subtypes of schizophrenia according to Andreasen's criteria. Blood samples were obtained from all patients for 2 consecutive days to determine plasma cortisol concentrations before and after a single administration (1 mg, p.o.) of dexamethasone at 11 p.m. The results revealed a significant increase in plasma cortisol levels in schizophrenic patients, with 40% of the patients being nonsuppressors on the dexamethasone suppression test. A higher percentage (62.5%) of patients with the negative form of schizophrenia were nonsuppressors.