Water excretion and plasma vasopressin in psychotic disorders.

To investigate the pathogenesis of water intoxication in psychotic disorders, a standard water load test was given to 23 unmedicated patients with schizophrenic or schizoaffective disorders. Levels of plasma arginine vasopressin were measured concurrently. Compared with 28 healthy volunteers, the psychotic patients had significantly smaller cumulative urine output and higher minimum urine osmolalities. Patients whose current illness had lasted less than 24 weeks exhibited the most severe antidiuretic state and also had the highest plasma arginine vasopressin levels. Water intoxication in acute exacerbations of psychosis may develop as a result of impaired excretory mechanisms.