Objectives: 1) To ascertain the stability of a diagnosis of compulsive water drinking (CWD) among psychiatric rehabilitation inpatients after a period of four years. 2) To ascertain the discharge status of CWD inpatients in comparison with matched control inpatients after a period of four years.

Method: A follow-up study was performed. Urine specific gravity testing was used to determine CWD status among psychiatric rehabilitation inpatients. Originally, 21 CWD subjects were identified, and 21 age and sex matched control subjects were selected from the non-CWD rehabilitation inpatients. Four years later those CWD and control subjects successfully traced (18 and 15 respectively) were retested for CWD. In addition each subject's living situation (inpatient or community resident) was recorded. Chi-square, Odds Ratio, and Fisher's Exact Test were used as tests of statistical significance.

Results: While the original CWD status was associated with the follow-up CWD status using Chi-square (p < 0.05), there was no statistical association using Odds Ratio (95% CI was 0.95 to 71.6). Half of the 18 original CWD subjects retested negative for CWD. Two of the 15 control subjects retested positive for CWD. Original CWD status was not associated with subsequent living situation, however all seven community dwelling subjects (four original CWD, three original controls) that were successfully traced were negative for CWD.

Conclusions: CWD status may not be as stable as implied in the literature.

Objective: To assess the importance of psychotropic medications in Compulsive Water Drinking (CWD) among psychiatric inpatients. Method: The psychotropic medication regimes of 21 CWD inpatients (16 of whom had a diagnosis of schizophrenia) and 21 age and sex matched control inpatients were compared. The CWD group was selected on the basis of urine specific gravity testing amongst the non-geriatric rehabilitation population of a Canadian psychiatric hospital. Regular and prn medications were compared by type and dose. Results: Both groups had generally similar regular medication regimes. No significant differences were found for any of the more commonly prescribed medications. There was a nonsignificant tendency for more CWD subjects to be given prn psychotropics, likely a consequence rather than a cause of the polydipsia. Conclusion: No significant differences were found between the two groups. However, because of the large number of medications used and the relatively small number of subjects, the study has relatively low power. A larger study, combining the CWD inpatients of several hospitals, would be required to definitely rule out a role for psychotropics in the aetiology of CWD.

Using urine specific gravity testing to estimate fluid intake Compulsive Water Drinking (CWD) was found to occur, without an age or sex bias, in 19.1% of rehabilitation inpatients in a Canadian psychiatric hospital. Chart review indicated that Water Intoxication had not been a major problem for these patients during their hospitalisation. Nursing opinion appeared to be a relatively weak test for CWD. In a comparison with age and sex matched control patients no significant association with alcohol abuse for the CWD patients or their relatives was found.