Post-traumatic stress disorder (PTSD) is an anxiety disorder that develops after a traumatic event. PTSD has also been called "shell shock" or "battle fatigue."

The exact cause of PTSD is unknown. PTSD is triggered by exposure to a traumatic event. Situations in which a person feels intense fear, helplessness, or horror are considered traumatic. PTSD has been reported in people who experienced:

  • War
  • Rape
  • Physical assault
  • Natural disaster such as earthquakes, hurricanes, or fires
  • Sexual abuse
  • Motor vehicle accidents
  • Animal attack

Researchers are studying how problems with synapses in the brain may be linked to PTSD.