So many of my friends and relatives of that era came back badly damaged. My own brother maintained systems on the "choppers" and wasn't in combat, but still dealt with some very hairy situations recovering parts from the downed copters. In retrospect, I've given a lot of thought to our father and his generation from WWII. Dad was in a couple of major battles and helped liberate a concentration camp. He carried a camera through most of the war(on his own, not professionally). I had assumed an horrific album from those camps (skeletal survivors and the dead piled like firewood) were his shots. I later learned a higher company officer had taken the photos and copied for his junior officers as a stark reminder. My dad was a handsome man and, by all accounts, previously very outgoing and witty. I saw occasional signs of the latter growing up, but mostly, he was strict and downright paranoid about me when I started dating. How this related to his past experiences was a puzzle. It just seemed part of his being a bit crazy in increasingly weird ways. He was convinced my mom was having an affair, to the point of her planning to divorce him at age sixty, just before his death.
If this seems a stretch in regard to PST, I can only add that several other people of my generation have told me similar stories about their fathers. Those guys would gather at the VFW or at one anothers' homes and tell rollicking stories of the WWII years. The ugly stuff was never mentioned,. This was only one factor making a difference after Viet Nam.