I don't know what studies there have been, if any. I mentioned the directorate of medical policy, which has a deployment health section that does that kind of research. As far as I know, no....
One thing I can say is that some studies have been done on symptomatology three to six months after deployment, starting six years after the Gulf War--deployment in Kabul in the early days of the mission and most recently deployment in Afghanistan. They looked at the percentages of troops who've returned and undergone this post-deployment enhanced screening. But remember, this is just screening, not diagnosis, and so far what we're finding is not alarming. In some cases, it's reassuring, in that it suggests that people are presenting much earlier. In other words, we're starting to beat the stigma, obstacles, and various disincentives to present for care early. That's a good thing, because the earlier they present for care, the less likely they'll carry on and develop a chronic condition.