PTSD doesn't have anything to do with brain damage.

PTSD is a trauma response.

Are you thinking of TBI? TBI is a cumulative impact of small and large head trauma.

Nope - I mean PTSD. there is a growing body of evidence that PTSD may be caused (In many of most or the diagnosed cases) by concussions causing brain damage. This manifests from either enemy munitions, or the shock wave from your own artillery, explosives, or large-caliber weapons.

The WWI name of "shell shock" describing the same phenomenon was probably more accurate than "PTSD".