About one in three people who have panic disorder develop agoraphobia, a condition that causes people to experience an overwhelming sense of fear that, in turn, causes them to avoid certain situations and places. In some cases, people who have agoraphobia become housebound, unable to perform normal, everyday activities, such as driving a car or grocery shopping. The condition is best treated with a specific form of short-term psychotherapy, in which the person is gradually exposed to certain situations and places that frighten them.