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Evaluation of abnormal behavior in the emergency department

J Stephen Huff, MD
Section Editor
Robert S Hockberger, MD, FACEP
Deputy Editor
Jonathan Grayzel, MD, FAAEM


Altered behavior ranges from subjective difficulty thinking clearly to abnormal thought content and states of depressed consciousness. When altered behavior directs the diagnostic workup, this implies that confusion, thought problems, or altered mental status is the chief complaint. Adjunctive complaints such as dyspnea, hypoxia, high fever, or acute focal neurologic deficits shift the clinician's approach.

Confusion is thought to be present in up to 50 percent of elderly hospitalized patients, 10 percent of all hospitalized patients, and 2 percent of emergency department patients [1].

The differentiation of abnormal behavior may be straightforward or complex. Sometimes no single explanation for altered mental status can be identified. Frequently, an acute medical illness exacerbates confusion in patients with dementia, essentially creating coexistent acute and chronic confusional states.

The focus of this review is the differentiation of acute medical and neurologic disorders from psychiatric causes of abnormal behavior in the emergency setting. The evaluation of the demented or agitated patient is discussed elsewhere. (See "Evaluation of cognitive impairment and dementia" and "Assessment and emergency management of the acutely agitated or violent adult" and "Diagnosis of delirium and confusional states".)


Altered behavior and confusion are terms without strict medical definitions. A "confused" patient frequently comes to medical attention because in the judgment of someone (family, caregiver, observers, or police) some behavior is deemed unusual for the individual or deviates from societal norms. Less commonly do patients complain of confusion, consistent with the frequent lack of insight into their altered behavior. Delirium is an acute change in attention and mental functioning, and the formal definition includes disturbance of wake-sleep cycles and fluctuating confusion. Dementia is a chronic confusional state with insidious onset. The two conditions can and frequently do coexist. (See "Evaluation of cognitive impairment and dementia" and "Diagnosis of delirium and confusional states".)

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Literature review current through: Nov 2017. | This topic last updated: May 23, 2017.
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