Posttraumatic stress disorder (PTSD) is an anxiety disorder that can develop after a person is exposed to one or more traumatic events, such as major stress, sexual assault, warfare, or other threats on a person's life. Symptoms include disturbing recurring flashbacks, avoidance or numbing of memories of the event, and hyperarousal, continue for more than a month after the occurrence of a traumatic event.Most people who have experienced a traumatizing event will not develop PTSD.