Overwhelming fright, fear, or terror, called panic, may happen to a person a few times in his or her life. During panic, you may feel like you are having a heart attack or that you are dying. Usually, panic is short-lived and is often related to a frightening event that happens to you. If panic occurs unrelated to situations, happens frequently, and is followed by at least 30 days of worry about another panic attack, this is termed panic disorder. Not every person who has a panic attack will develop panic disorder. There is evidence that panic disorder is sometimes genetic (inherited). Along with the other types of anxiety disorders (obsessive-compulsive disorder, generalized anxiety disorder, social anxiety disorder, posttraumatic stress disorder, and phobias), panic disorder is fairly common. Anxiety disorders affect more than 40 million adults in the United States alone, about 18% of the population. Worldwide, approximately 20% of persons who receive primary health care have anxiety disorders or depression.