PTSD is largely a brain rewiring in response to being in a situation where you were helpless in the face of existential danger. This can be readily be duplicated in a number of mammals, and was first proven in dogs following the partial flooding of a lab. PTSD leads to fight/flight/freeze responses to that stimuli later on. Anger isnt so much a "this was pointless" reaction as a fight response. Fortunately PTSD can be treated, largely through talk therapy to fully explain what happened, why it happened, why it was traumatizing, and why you were indeed helpless to protect yourself from the existential danger. Which is difficult because you need a safe, understanding community to do that in. Which is hard to find because people who grok PTSD and people who live in a close knit Mayberry-esque community rarely overlap. Throwing pills at it doesnt help for the same reason morphine doesnt help toothaches - it just numbs you out without treating the root cause.