Interesting article in the Times about Daniel Perl, a Neuro-Pathologist who thinks much Post-Traumatic Stress Disorder is caused by physical damage to the brain, possibly from explosive shock waves. It's intriguing, and it would explain one of the most puzzling things about PTSD: why does it seem to be so much more common in soldiers of the modern era than it ever was before?
On the other hand, I would point out that PTSD affects many soldiers who have not been exposed to big explosions, and in fact many who have never been in combat at all. So it is unlikely to be the whole story. But I would not be at all surprised if it turns out to be a big part of the story.