Definition and Epidemiology

Anxiety is defined as an unpleasant emotional state consisting of psychologic and physiologic responses to the anticipation of real or imagined danger.¹ Regardless of whether the observed disease prevalence is related to the escalating complexity and stress of traumatic events and modern life, evolving access to medical and behavioral health care, the inherent nature of the emergency department (ED), or an increased awareness of psychiatric disorders, anxiety is common in patients who seek emergency care.^2,3

In the United States, anxiety disorders have a 12-month prevalence of 18% and a lifetime prevalence that approaches 25%. Anxiety-related conditions cost more than $42 billion in medical expenses and lost worker productivity in 1990 alone.^4–6 Patients with anxiety disorders use outpatient and emergency care more often and generate higher medical costs than do patients without anxiety disorders.⁷

Anxiety disorders are increasingly being seen in urban EDs and, particularly panic disorder, occur more frequently in women than in men.^3,8 These conditions are the most common psychiatric illnesses diagnosed in children, adolescents, and older adults.^9,10 Anxiety disorders may significantly affect a patient’s quality of life and overall health. Anxiety is commonly associated with depression, other mood disorders, and substance abuse.

Numerous potentially life-threatening medical disorders feature symptoms that often mimic anxiety on initial evaluation. Emergency physicians must be able to discern such serious medical conditions from a principally anxious patient.

Pathophysiology

Anxiety disorders are caused by a combination of biologic factors and environmental influences.¹¹ Despite increased basic science and clinical research, a specific explanatory mechanism or model to describe the exact causes of anxiety has yet to be identified.

The genetic epidemiology of anxiety disorders has been confirmed by numerous studies and metaanalysis. Most anxiety disorders have significant familial aggregation, and the inheritability of panic disorder approaches a rate of 40%.¹²

Several neurotransmitters play integral roles in the pathophysiology of stress and mood and anxiety disorders. Decreased γ-aminobutyric acid and serotonin receptor sensitivity are common in most anxiety disorders. Overactivity of the central norepinephrine system and elevated sensitivity to lactate and carbon dioxide are prominent findings in panic disorder. Cholecystokinin and increased excitatory neurotransmission by glutamate may contribute to the evolution of conditioned fear.^13,14 Evolving research suggests that dopamine and corticotropin-releasing factor play a role in both mood and anxiety disorders.^14,15

An environmental factor is integral to the development of anxiety. Stressful childhood experiences, such as abuse and divorce, contribute to generalized anxiety and panic disorders.¹¹ Caffeine and other socially accepted stimulants (e.g., taurine, ginseng), as well as recreational substances (e.g., cocaine, methamphetamine, γ-hydroxybutyrate, jimson weed, salvia), often promote symptoms of anxiety.^16,17 Finally, increasing exposure to violence, natural disasters, terrorism, and other traumatic events has caused greater numbers of people to suffer from acute stress reactions, anxiety, depression, and posttraumatic stress disorder.^18,19

Clinical Presentation

Anxiety may be accompanied by many somatic and cognitive signs and symptoms, as listed in Box 197.1.^9,10,20 The physical symptoms of acute anxiety are similar to those of excitation, such as chest pain, dry mouth, dyspnea, lightheadedness, and palpitations. Symptoms of subacute or chronic anxiety include fatigue, insomnia, and menstrual abnormalities. An anxious patient may have normal findings on physical examination or may exhibit tachycardia, tachypnea, and diaphoresis.

Psychologic symptoms of anxiety include distractibility, emotional lability, noncompliance, and recurrent or obsessive thoughts. An anxious patient may be easily startled, demonstrate pressured speech, or suffer repetitive behavior.