Psychogenic polydipsia and water intoxication--concepts that have failed.

Ten patients (8 men, 2 women; mean age 38.7 +/- 8.1 years), 7 of whom had schizophrenic disorders and 3 of whom had bipolar disorder (manic-depressive illness), manifested psychosis, intermittent hyponatremia, and polydipsia (PIP syndrome). The relationship between serum sodium and urinary water excretion among the 10 PIP patients is described in detail. The success of lithium in improving serum sodium levels and in decreasing urinary water excretion among the three PIP patients with bipolar disorder and the failure of changes in urinary water excretion to explain changes in serum sodium levels among the 10 PIP patients argue against "psychogenesis" as the explanation for the polydipsia and excessive water intake as the sole explanation for hyponatremia or complications ascribed to water intoxication.