Xerostomia , a feeling of dry mouth, is often caused by medications. Common nonpsychotropic causes are other medications (e.g., decongestants, diuretics), substance use (e.g., tobacco, methamphetamine), and excessive mouth breathing (as in nasal congestion). Less common causes are chemotherapy, radiation therapy, and Sjogren’s syndrome . In addition to oral discomfort, a complication of dry mouth is dental caries.