The study that I read from The New England Journal of Medicine actually captures a population of people who are injured, and then it separates out from those the people who had some kind of head injury with sequelae--so concussion, if you want. Then it looks at that population and says, okay, what's the incidence or prevalence of post-traumatic stress disorder in that group? And lo and behold, I think it was around 40% of the people with significant concussion had post-traumatic stress disorder.
I wondered when I was reading that study if that was a proxy to being close to combat and close to danger, which is the risk for post-traumatic stress disorder, right? So if you have an explosion significant enough to knock you out and your life is in danger, you pretty well have criteria A of post-traumatic stress disorder, a psychological trauma, down there. So I think that might be what it's predicting.