Misdiagnosing Delirium as Depression in Medically Ill Elderly Patients

Background: Delirium, a common and often overlooked syndrome in acutely ill elderly patients, may present with signs and symptoms of depression. Objective: To determine (1) how often health care providers mistake delirium for a depressive disorder in older hospitalized patients referred to a psychiatric consultation service for depressive symptoms and (2) which signs and symptoms of depression and delirium characterize these patients. Subjects: Patients older than 60 years, admitted to a Veterans Affairs teaching hospital, and consecutively referred to a psychiatric consultation service for evaluation and treatment of a depressive disorder. Methods: The diagnosis of delirium was based on two independent assessments: (1) a clinical interview by a member of the psychiatric consultation service and (2) a structured bedside evaluation performed by one of the investigators, who was not a member of the psychiatric consultation service. The investigator administered the Confusion Assessment Method Instrument, Mini-Mental State Examination, digit span forward, and months of year backward. The investigator also administered the Diagnostic Interview Schedule items for depression to elicit depressive symptoms. Results: Twenty-eight (41.8%) of the 67 subjects referred for evaluation or treatment of a depressive disorder were found to be delirious. Compared with nondelirious subjects, the delirious subjects were older and more impaired in activities of daily living. The delirious subjects often endorsed depressive symptoms, such as low mood (60%), worthlessness (68%), and frequent thoughts of death (52%). The referring health care provider had considered delirium in the differential diagnosis of the mood disturbance in only three subjects. Conclusion: Health care providers should consider the diagnosis of delirium in hospitalized elderly patients who appear to be depressed.