Agoraphobia is an anxiety disorder characterized by anxiety in situations where the sufferer perceives the environment to be dangerous, uncomfortable, or unsafe. These situations can include wide-open spaces, uncontrollable social situations, unfamiliar places, shopping malls, airports, and bridges. Agoraphobia is defined within the DSM-IV TR as a subset of panic disorder, involving the fear of incurring a panic attack in those environments. In the DSM-5, however, agoraphobia is classified as being separate from panic disorder. The sufferers may go to great lengths to avoid those situations, in severe cases becoming unable to leave their homes or safe havens.