Anxiety disorders refer to a cluster of anxiety problems, including panic disorder (panicky sensations that appear suddenly, and often without an obvious trigger), generalized anxiety disorder (GAD) (feeling anxious all the time, without a specific source, but can generally be traced back to at least two life events that occur during the six months that the person has the anxious feelings), social or specific phobias (fear of certain objects and social situations), obsessive-compulsive disorder (OCD) (anxiety over uncontrollable thoughts and compulsions), and post-traumatic stress disorder (PTSD) (anxiety over a traumatic experience). The dominant feelings that cut across these disorders are anxiety and fear.