Post Traumatic Stress Disorder (PTSD) is an anxiety disorder that can develop after experiencing or witnessing a major trauma. Children and teens with PTSD can have a number of symptoms after a trauma that fall into three categories: (1) Reliving the trauma in some way; (2) Attempts to avoid anything that reminds the child or teen of the trauma; (3) Very high anxiety (also called "hyperarousal") and being easily startled. Children and teens with PTSD usually have some symptoms from each of these categories.