Some of the U.K. folks tried to look at this. At this point, there isn't any evidence that pre-screening.... It makes a lot of sense to do some cognitive therapy or some skills building that helps build resilience prior to deployment. Those kinds of studies are actually very important and necessary, but they haven't been done.
The question of whether training somebody prior to deployment would protect them from getting mental illness is a question that's been asked for a number of years, but no one's actually done a study on that.
What we do know, in general, about what puts people at risk for mental illness and suicide is that suicide is even more difficult to prevent in this kind of way, because suicide is of much lower prevalence than PTSD and depression.
It's very hard to look at that. But people who have gone through a lot of childhood adversity or who have a family history of mental illness and have a genetic loading for it are at the highest risk, generally, of mental illness if there's a stressor in their lives or a relationship loss. But I think it makes it very difficult to screen people out because of that.