Put yourself in the following situation: you're speeding along a highway when suddenly a deer crosses in front of you. You pull the steering wheel hard trying to avoid the animal. The car swerves and spins off into the emergency lane, and you skid to a stop. Somehow you've managed to avoid a potentially fatal accident—for both you and the deer.

You're shaking, your heart is racing, and you've broken out into a quick and cold sweat. But you're alive! This would be the normal reaction for most people in a similar situation.

Now imagine this: you're at a restaurant having a quiet dinner when suddenly, for no apparent reason, you experience the same uneasy feelings. You begin shaking, your heart starts racing, and you break out into a cold sweat. You even feel like you might be having a heart attack. You're rushed to the hospital, and the doctors can find nothing immediately wrong with you.

What These Symptons Mean

You may have experienced a panic attack—and a few of the typical symptoms usually associated with panic disorder.

A panic attack seems to come out of nowhere—at times and in places where there is nothing to fear. When experiencing the effects of the attack, you may think you're having a heart attack, dying, or even going crazy. But in reality, there is nothing wrong with your heart—or your sanity. You're simply one of the millions who suffer from this frightening and debilitating disorder.

What Is Agoraphobia?

Some people with panic disorder also have agoraphobia.

Agoraphobia is an anxiety—or a fear—of being in places or situations from which escape might be difficult (or embarrassing) or in which help may not be available in the event of having a panic attack or panic-like symptoms (for example, fear of having a sudden attack of dizziness or a sudden attack of diarrhea). Some people with agoraphobia may fear being outside the home alone; being in a crowd or standing in a line; being on a bridge; or traveling in a bus, train, or car.

Situations like these may be avoided, or else they're dreaded—and then endured. Typically, this means staying away from places or circumstances where previous experiences have happened. Obviously, having such a "fear of the fear" can make normal everyday life impossible.

How Common are These Symptoms?

According to the National Institute of Mental Health, approximately 6 million Americans aged 18 and older suffer from panic disorder in a given year. That's about 2.7% of the adult US population. About one-third of those develop agoraphobia—fear of being in public places.

Panic disorder typically strikes in young adulthood, beginning in the late teen years or early to mid-20s. About half of all people who have panic disorder develop it before the age of 24. Although a panic attack is spontaneous and unexpected in most cases, sometimes a stressful event such as a divorce or death of a parent can also trigger an attack.