Most people who go through a trauma have some symptoms at the beginning. Only some will develop PTSD over time. It isn’t clear why some people develop PTSD and others don’t.

Whether or not you get PTSD depends on many things:

  • How intense the trauma was or how long it lasted
  • If you were injured or lost someone important to you
  • How close you were to the event
  • How strong your reaction was
  • How much you felt in control of events
  • How much help and support you got after the event

From the National Center for PTSD, US Department of Veterans Affairs. http://www.ptsd.va.gov/public/pages/what-is-ptsd.asp