Pain perception is designed to help us recognize threats to our survival. The perception of pain, of all varieties, is actually created in our brain as a result of stimuli, which can come from a number of different sources such as nerve cells in the skin, perceptions from sensory inputs (hearing, smelling, tasting, etc.) or even from memories.
Symptoms of PTSD are at the end of a continuum of resiliency. A clearer understanding of how the brain operates in the face of trauma - both physical and emotional - can mitigate a tremendous amount of suffering.
Post Traumatic Stress Disorder (PTSD) can occur from any traumatic event whether witnessed or experienced.