I clearly found this more compelling than did those who have commented, above.
I think we did see the effects of PTS: the image of the girl pulled from the rubble was, at least in my mind, quite horrific, yet the men were entirely unfazed. And, to add to the horror, Stan knew that he *should* be feeling something -- he explicitly recognised that he had lost his humanity, that it had been torn away from him by his experiences.
Perhaps I missed something, but I found the repeated references to parapsychology in the outro a bit of a non sequitur. I really enjoy the horror genre, and perhaps not primarily as a form of entertainment but rather because the responses it elicits, I think, provide important and fascinating insights into the human psyche. Horror fiction has real value. There is real value in thinking seriously about ghouls and ghosts, in an effort to understand ourselves. Whereas parapsychology -- the pseudoscientific study of ghouls and ghosts -- has zero value, as far as I can see. I do not see parapsychology as the scientific equivalent of horror fiction. Fiction is fiction, science is science, neither claims to do the work of the other. Parapsychology is make-believe masquerading as science, it's a waste of time and resources.
Yes, ghouls and ghosts are worthy of empirical, scientific study, because they are real-world phenomena insofar as they manifest in our minds and our culture. But that falls within the remit of proper, rigorous disciplines like psychology and anthropology: a world away from ESP, astrology and homeopathy.