• The brainstem, which controls some of the physical "fight or flight" symptoms

• The limbic system, which deals with anxiety and other emotions

• The prefrontal cortex, which instructs the body to avoid fearful situations

Also, it is possible that people with panic disorder may have inherited a "fight or flight" response that is either more sensitive than normal or that responds more intensely than usual. Studies of close relatives of people with panic disorder show that this disease has a genetic (inherited) basis. These relatives are four to eight times more likely to develop the illness than people with no family history of the problem.

In the United States, panic disorder affects an estimated 1.5% to 3.5% of people at some point during their lives. Women are two times more likely than men to have panic disorder, and about three times more likely to develop agoraphobia. On average, symptoms start at around age 25, but panic disorder and agoraphobia can affect people of all ages.

Some people with panic disorder first develop symptoms after a stressful life event, such as divorce, job loss or a death in the family. Scientists still do not understand exactly how panic attacks are triggered, but there is growing evidence that stress in early life increases a person’s vulnerability to developing panic symptoms. Also for unknown reasons, people who have panic disorder have an extraordinarily high risk of developing other types of psychiatric problems. In fact, at the time of diagnosis, more than 90% of people with panic disorder also have major depression, another anxiety disorder, a personality disorder or some form of substance abuse.

Symptoms

A panic attack is defined by having at least four of the following symptoms:

• Palpitations, heart pounding or a rapid pulse

• Sweating

• Trembling or shaking

• Breathing problems, especially shortness of breath or a feeling that you are being smothered

• A feeling of choking

• Chest pain or chest discomfort

• Abdominal discomfort, upset stomach or nausea

• Feeling faint, dizzy, lightheaded or unsteady on your feet

• A feeling that things around you are unreal or that you are detached from yourself

• Fear that you will lose control or "go crazy"

• Fear of dying

• Numbness or tingling in your arms, legs or other parts of your body

• Chills or hot flushes

Between panic attacks, someone with panic disorder usually has persistent worries that a new attack will occur. These worries may cause the person to dramatically change his or her behavior or lifestyle to avoid the embarrassment of "losing control" or "going crazy" while with other people.