How is panic disorder related to agoraphobia and phobic avoidance?

Often those affected with panic disorder will become anxious about having panic attacks in certain public places or situations where they have had them before. This causes them to deliberately avoid those situations or places, a behavior known as phobic avoidance. About one-third of those with panic disorder develop agoraphobia, an extreme form of public avoidance. Many people with agoraphobia grow so afraid of being out in public that they become housebound.