What is the prevalence range of antidiuretic hormone dysfunction in schizophrenia?

• A. 1-2%
• B. 6-20%
• C. 25-35%
• D. 40-50%

Answer: (B)

Antidiuretic hormone dysfunction in schizophrenia is most often understood as SIADH-related hyponatremia, where too much ADH causes the body to retain water and dilute the blood’s sodium. In people with schizophrenia, this dysfunction is not rare but not extremely common either, with studies typically showing a prevalence in the 6-20% range. This range best fits what is observed clinically: it’s a meaningful minority of patients who develop hyponatremia due to ADH excess, without suggesting it affects a majority of patients.

This matters because hyponatremia can cause symptoms from confusion and dizziness to seizures and, in severe cases, coma. The risk is higher in patients who are on medications that can elevate ADH activity (some antipsychotics, antidepressants, or other drugs) or who have other risk factors like older age or coexisting medical conditions. So the 6-20% range reflects the balance between being clinically significant and not describing the complication as ubiquitous.