Water Intoxication and Syndrome of Inappropriate Secretion of Antidiuretic Hormone in Schizophrenic Patients Evaluated by Water Deprivation and Load Tests

A study was conducted on 16 schizophrenic patients with compulsive water drinking (CWD) and 10 normal controls, and the relation between serum antidiuretic hormone (ADH) and serum osmolality measured under ordinary conditions of free water intake. A water deprivation test and a water load test were also carried out on 10 schizophrenics with CWD and 10 normal controls. A comparison between the patients and controls showed the following results: the patients showed a significantly high level of serum ADH for their serum osmolality level, and 3 of them were consistent with the syndrome of inappropriate secretion of ADH (SIADH); the urine osmolality after the water deprivation in the patients was relatively low for their serum ADH; inhibition of ADH secretion after the water load was insufficient in the patients; and the water load test proved favorable to water diuresis (106%) in the patients with CWD of less than a 5-year duration, and insufficient diuresis (62.6%) in the patients with CWD of more than a 5-year duration. Two cases of the latter group had SIADH. The dilution and concentration of the urine after the water load were delayed also in the schizophrenic patients without SIADH. These findings suggest a strong possibility that the regulatory mechanism of ADH secretion might be impaired in the schizophrenic patients with CWD.