Between 1986 and 1998, a review of 61 records of patients who died before the age of 53 years in eight psychiatric departments whose catchment area had a total population of 559,429 inhabitants revealed that 24 (39.3%) of those patients had a schizophrenic disorder. Of those 24 patients, one (4.17%; 95% CI: 0–21%) died from complications of self-induced water intoxication (SIWIS). Among the 37 remaining patients, two (5.4%; 95% CI: 0–18%) died from complications of SIWIS.

Maximization theory, which is borrowed from economics, provides techniques for predicing the behavior of animals - including humans. A theoretical behavioral space is constructed in which each point represents a given combination of various behavioral alternatives. With two alternatives - behavior A and behavior B - each point within the space represents a certain amount of time spent performing behavior A and a certain amount of time spent performing behavior B. A particular environmental situation can be described as a constraint on available points (a circumscribed area) within the space. Maximization theory assumes that animals always choose the available point with the highest numerical value. The task of maximization theory is to assign to points in the behavioral space values that remain constant across various environmental situations; as those situations change, the point actually chosen is always the one with the highest assigned value.

Maximization theory is an alternative to reinforcement theory as a description of steady-state behavior. Situations to which reinforcement theory has been directly applied (such as reinforcement of rats pressing levers and pigeons pecking keys in Skinner boxes) and situations to which reinforcement theory has occasionally been extended (such as human economic behavior and human self-control) can be described by maximization theory. This approach views behavior as a quantitative outcome of the interaction of the putative instrumental response, the reinforcer, and the other activities available in the situation. It provides new insight into these situations and, because it takes context into account, has greater predictive power than reinforcement theory.

This case report is of a young male with learning disability, who presented with long-term polydipsia and hyperphagia. The patient's polydipsia and hyperphagia showed a correlation with long-term use of neuroleptics for behavioural problems. Withdrawal of all neuroleptic medication resulted in an immediate improvement in both the polydipsia and hyperphagia leading to a complete resolution of both symptoms. While neuroleptics are a recognised cause of polydipsia, hyperphagia is less frequently described and we believe this to be the first report in which a patient is observed to have polydipsia and hyperphagia induced by neuroleptics. We discuss the possible aetiological mechanisms for both polydipsia and hyperphagia and conclude that the basic pathophysiology in our case appears to be a neuroleptic induced malfunction of the satiety centre due to blockage of dopamine receptors in the ventromedial hypothalamus.

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.

Objectives: The objectives of this paper are to review the presentation of hyponatraemia and diagnose its cause in psychiatric inpatients.

Method: Episodes of significant hyponatraemia (sodium <130mmol/L) were identified from computerised biochemical data and a retrospective review of patients' notes was carried out.

Result. The diagnoses of hyponatraemia reached were different for the two groups of patients studied, adults of over 65 years and under 65 years. Carbamazepine, polydipsia and medical conditions were found as causes in the below 65 age group. Diuretics, medical conditions and lofepramine were identified as causes in the over 65 age group. Inpatients with polydipsia below the age of 65 had lower sodium (p = 0.013) and urea levels (p = 0.00059) than other groups and patients with carbamazepine induced hyponatraemia tended to have episodic hypocalcaemia (p = 0.056). These groups were compared using Fisher's exact test. This study also showed the overall frequency of serum sodium of less than 135mmol/L to be 9.5% in psychiatric inpatients.

Conclusion: Hyponatraemia is a not uncommon finding in psychiatric inpatients. Attention to drug therapy and biochemical findings are helpful in its diagnosis. Accurate diagnosis is usually possible and may vary according to age-group.

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.