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.