ABSTRACT
There appeared remarkably common disorder of water balance in psychiatric patients. Approximately 30% of the chronic inpatient population drinks fluids excessively, so called polydipsic, while 5% suffers episodes of water intoxication. Water intoxication is a serious problem characterized by profound hyponatremia and a diverse neurologic signs ranging from ataxia, confusion to death. The cause of polydipsia is even less clear. Although previous studies have suggested that it is related to cognitive dysfunction the possibility of an abnormality in the osmoregulation of thirst has not been investigated. But there is the hypothesis that polydipsic, hyponatremic schizophrenics exhibit increased neuroendocrine and behavioral sensitivity to dopamine in mesolimbic tracts, in proportion to the severity of their osmoregulatory disturbance. In order to provide the optimal clinical management of these common disturbances, the author will review their pathophysiology, assessment, treatment and relationship with mental illness.