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Key Points

  • New-onset psychiatric illness requires a comprehensive emergency department work-up. Consider a medical etiology.

  • Prior psychiatric illness with similar presentation does not require an extensive work-up.

  • Agitated patients need immediate treatment in the emergency department.

  • Patients with suicidal and homicidal plans or inability to care for themselves need psychiatric admission.


Psychiatric illness is a common presentation to emergency departments (EDs). The number of psychiatric patients presenting to EDs has increased both in total number and in percentage of total ED visits, from 4.9% to 6.3% from 1992–2001. The main ED psychiatric diagnoses are substance-use disorders (22%), mood disorders (17%), and anxiety-related disorders (16%).

Patients with psychiatric illness may have various presentations depending on their underlying psychiatric diagnosis as well as their concurrent medical condition. Psychiatric patients may present with depressed affect, psychosis, agitation, suicidal or homicidal ideation, catatonia, delusions, or dementia.

Like other conditions presenting to the ED, the emergency physician must determine whether the patient has a life-threatening condition. The life-threatening conditions include suicidal or homicidal plans and medical condition masquerading as psychiatric illness (Table 98-1). Frequently identified medical causes of abnormal behavior include hypoglycemia, hypoxia, seizures, head trauma, and thyroid abnormalities. Patients should also be assessed for the presence of delirium or dementia, as both have potentially treatable causes. The primary role of the ED physician is to determine whether the psychiatric presentation is due to a medical or psychiatric etiology. This determination is often referred to as the medical clearance process. The secondary role of the ED physician is to evaluate the patient's coexisting medical conditions because many of these psychiatric patients have a high incidence of medical illnesses that have been neglected.

Table 98-1.

Medical conditions that masquerade as psychiatric disease.

Some psychiatric patients present to the ED with acute agitation. These patients, like others in the ED, are acutely ill and need to be stabilized before definitive evaluation can be completed. Once the agitation has been reduced, the clinician must determine the cause of the agitation and the need for a psychiatric versus medical admission.

Clinical Presentation


A detailed history, including prior psychiatric history, is the most important step to determine whether the patient's presentation is due to a medical or psychiatric problem. It is important to determine whether the patient's current presentation is the same or similar to previous psychiatric presentations. Some psychiatric patients can provide a history of their condition, whereas others may require collateral information. History from family, bystanders, paramedics, police ...

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