Polydipsia--a study in a long-term psychiatric unit.

This is a retrospective review of the author's experience with polydipsia in a long-term unit for treatment refractory patients at a US psychiatric state hospital during a 5-year period [1996-2000]. Sixty-one patients were admitted to this long-term unit, comprising approximately 1 % of the hospital admissions. Polydipsic patients were followed with diurnal weight changes and other biological measures. This longitudinal study of 61 chronic inpatients suggests that polydipsia is no doubt present in at least 20 % of chronic psychiatric inpatients and hyponatremia in more than 10 %. Two polydipsic patients worsened when switched from clozapine to other atypical antipsychotics. Polydipsia in severe mentally ill patients continues to be a neglected subject and a challenge for psychiatrists. Polydipsic patients should not be switched to other atypical antipsychotics, unless new prospective studies prove that they are as effective as clozapine for polydipsia.