Hi Scott,
I'm sorry that it took so long to reply, but I have been computerless at home since last week.
I was a Social Worker for many years and was suprised to find that Civil War soldiers also suffered from PTSD. I read a book several years ago called "Shook over Hell", about PTSD and Civil War Era. It's by Eric Dean and can be gotten through your library interloan. He spoke to my Civil War Roundtable.
One theory that I have is that the previous generations had more experience with death before going to the front to the front than the newer generations. There was a higher child mortality rate. People also did not survive as long and were waked at home. Today, I have friends who are in their 50's and still have both parents alive as well as a grandparent.