Introduction
Anxiety disorders involve a state of distressing chronic but fluctuating nervousness that is inappropriately severe for the person's circumstances.
Anxiety is a normal response to a threat or to psychologic stress and is experienced occasionally by everyone. Normal anxiety has its root in fear and serves an important survival function. When someone is faced with a dangerous situation, anxiety induces the fight-or-flight response. With this response, a variety of physical changes, such as increased blood flow to the heart and muscles, provide the body with the necessary energy and strength to deal with life-threatening situations, such as running from an aggressive animal or fighting off an attacker. However, when anxiety occurs at inappropriate times, occurs frequently, or is so intense and long-lasting that it interferes with a person's normal activities, then it is considered a disorder.
 See the figure How Anxiety Affects Performance.
Anxiety disorders are more common than any other category of mental health disorder and are believed to affect about 15% of adults in the United States. However, anxiety disorders often are not recognized by people who have them or by health care professionals and consequently are seldom treated.
Causes
The causes of anxiety disorders are not fully known, but both physical and psychologic factors are involved. Because anxiety disorders are prevalent in some families, heredity probably plays a role. Anxiety is viewed at a psychologic level as a response to environmental stresses, such as the breakup of a significant relationship or exposure to a life-threatening disaster. When a person's response to stresses is improper or a person is overwhelmed by events, an anxiety disorder can arise. For example, some people find speaking before a group exhilarating, while others dread it, becoming anxious with symptoms such as sweating, fear, rapid heart rate, and tremor.
Anxiety disorders may also be caused by a physical disorder or the use of a drug. For example, an overactive thyroid gland, use of prescribed corticosteroids, or illicit use of cocaine may produce symptoms of an anxiety disorder.
Symptoms and Diagnosis
Anxiety can arise suddenly, as in panic, or gradually over minutes, hours, or days. The anxiety itself can last for any length of time, from a few seconds to years. Anxiety ranges in intensity from barely noticeable qualms to full-blown panic attack (see Section 7, Chapter 100), during which a person may experience shortness of breath, dizziness, and increased heart rate.
Anxiety disorders can be so distressing and interfere so much with a person's life that they can lead to depression (see Section 7, Chapter 101). Sometimes depression develops first and an anxiety disorder develops later.
The diagnosis of an anxiety disorder is based largely on its symptoms. The ability to tolerate anxiety varies, and determining what constitutes abnormal anxiety can be difficult. A family history of an anxiety disorder (except posttraumatic stress disorder) may help a doctor make the diagnosis.
Treatment
Accurate diagnosis is important, since treatment varies from one anxiety disorder to another. Additionally, anxiety disorders must be distinguished from anxiety that occurs in many other mental health disorders, for which different treatment approaches are used. Depending on the anxiety disorder, drug therapy or psychotherapy (such as behavior therapy), alone or in combination, can significantly relieve the distress and dysfunction for most people.
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