Post Traumatic Stress Disorder (PTSD) can develop in children and teens 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) Attempting to avoid anything that reminds the child or teen of the trauma, or 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.