I have read the interesting article1 that Dr Yium coauthored. It reports on a retrospective record review of ten patients with schizophrenia and hyponatremia. Eight of these ten patients were described as excessive water drinkers. Six of the eight polydipsic patients were smoking more than one pack of cigarettes a day. The hyponatremic patients were compared with a group of normonatremic schizophrenics and in regard to their smoking habits, no significant difference was found. However, there are unavoidable limitations to a retrospective study, and in addition, none of the normonatremic control group patients were polydipsic. Cigarette smoking is expected to cause hyponatremia by ADH-induced renal water retention only in case of simultaneous excessive hydration, as in polydipsia.I agree with Dr Yium that before drugs or hypothetical neuroendocrine dysfunction of schizophrenia are considered as causes of hyponatremia in polydipsic patients, etiological assessment of cigarette smoking—so prevalent among
Blum A. Tobacco Smoking and Hyponatremia in Psychiatric Patients-Reply. JAMA. 1985;253(20):2959. doi:10.1001/jama.1985.03350440037013
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