Comparison of severe hyponatremia in patients with and without psychiatric diseases: A single‐center retrospective study

Aims: Hyponatremia is a common electrolyte disorder. The severe hyponatremia has a mortality rate of 4%-40%. Psychiatric patients are likely to develop the condition because of polydipsia or the adverse effects of antipsychotics. We investigated the characteristics of patients with and without psychiatric diseases who developed severe hyponatremia. Materials and Methods: We retrospectively investigated cases admitted to our hospital (all departments) between October 2012 and November 2015 with a serum sodium concentration of ≤125 mmol/l on admission. We compared patient characteristics, etiology, and clinical course between psychiatric and nonpsychiatric patients. Results: = 9). The mean patient age was 63 years. The mean serum sodium concentration on admission was 119 mmol/l, and the main causes of hyponatremia were polydipsia (20%), insufficient sodium intake (18%), and syndrome of inappropriate antidiuretic hormone secretion (16%). Compared with the nonpsychiatric group, the psychiatric group was significantly younger (55 vs. 74 years), was more likely to have polydipsia (30% vs. 6%), and had a lower in-hospital mortality (0% vs. 17%). Conclusions: Our study found differences in the clinical picture between psychiatric and nonpsychiatric patients with severe hyponatremia. Clinicians need to monitor serum sodium because the symptoms of hyponatremia can mimic those of psychiatric diseases.