Neuropsychiatric patients with underlying central nervous system (CNS) disturbance can present to the emergency department because of a change in behavior. A detailed and accurate history is obtained from anyone who presents with a cognitive, behavioral, emotional, or other neuropsychiatric disturbance. In neuropsychiatric evaluation, the mental status examination is of paramount importance. The possibility of alcohol or illicit drug use is investigated thoroughly in any patient who presents with acute mental status or behavioral changes. Acute symptoms may be caused by worsening of a neurological or medical condition or by another underlying neuropsychiatric condition. Chronic neuropsychiatric symptoms that worsen are commonly associated with psychosocial stressors and a related adjustment disorder. Certain conditions of a psychiatric nature, including destructiveness, disorganization, depression, disorientation due to severe organic mental disturbances, and conditions requiring detoxification, require psychiatric hospitalization, whether or not the patient has an underlying CNS disturbance.