Polydipsia and water intoxication in psychiatric patients: a review of the epidemiological literature.

Polydipsia among chronic psychiatric patients is poorly understood and underdiagnosed. It may have three stages: simple polydipsia, polydipsia with water intoxication, and physical complications. Epidemiological surveys have used staff reports and polyuria measures to identify polydipsic patients. Water intoxication has been screened by chart review, weight, or serum sodium data. According to these surveys, polydipsia, not explained by medically induced polyuria, may be present in more than 20% of chronic inpatients. Up to 5% of chronic inpatients had episodes of water intoxication although mild cases may have been missed. Single time point surveys show that 29% of polydipsic patients had presented water intoxication. Methodologically limited clinical studies suggest that polydipsia with water intoxication rather than simple polydipsia may be associated with poor prognosis in schizophrenia. Epidemiological surveys found polydipsia with water intoxication to be associated with chronicity, schizophrenia, smoking, some medications, male gender, and white race. New pathophysiological models need to elucidate these findings.