A completely underrated author on trauma is C. Fred Alford. PTSD morphed from a diagnosis for soldiers returning from Vietnam to encompass everything. Life is traumatic. Everyone you know and love will die, and you will die. We also individually react differently to traumatic experiences, and a life changing positive moment for one person could destroy another.

https://traumatheory.com/time-to-drop-ptsd/

The really interesting discovery made about trauma in veterans is

https://en.wikipedia.org/wiki/Moral_injury