According to several authors, water intoxication can lead to irreversible brain damage and could be the cause of nearly a fifth of the deaths of schizophrenic patients below the age of 53 years. The aim of our study was first to determine the prevalence of polydipsia and water intoxication in a population of psychiatric inpatients of a well-defined French geographic area (the Somme), and secondly to determine the clinical and socio-demographic factors associated with this disorder.

A cross-sectional survey was done on the 450 psychiatric beds whose catchment area had a total population of 559,429 inhabitants. Using staff reports and patients’ charts, the drinking habits of 353 psychiatric inpatients hospitalised during the survey in the 450 psychiatric beds of this area were examined.

Thirty-eight patients (10.76%; 95% confidence interval: 7.53–13.99%) among the 353 inpatients were polydipsic. About one-third of these patients were at risk of water intoxication. Polydipsia appeared to be significantly associated with male gender, smoking, celibacy and chronicity. The polydipsic patients presented also a high prevalence of schizophrenia, mental retardation, pervasive developmental disorders and high frequency of somatic disorders.