To the Editor.—
The recent article by Matuk and Kalyanaraman (Arch Neurol 34:374, 1977) on the syndrome of inappropriate antidiuretic hormone (ADH) secretion in patients treated with psychotherapeutic drugs raises certain unanswered questions regarding ADH activity in schizophrenic patients, as well as the effect of neuroleptic medications on the release of ADH. They state that it was the medications their patients received (thioridazine, haloperidol) that caused the syndrome of inappropriate ADH release to develop. However, another explanation is that the medications were not involved directly, but rather the schizophrenia itself, or perhaps some unknown factor, that induced the inappropriate secretion of ADH.Disturbances of water metabolism, including the consumption of large amounts of water, have been described in association with various psychiatric disorders.1-4 In the prephenothiazine era, clinical studies showed that the urinary output of the schizophrenic population was two to three times that of the normal population.5