PTSD is a formal diagnosis, and operational stress injury is not. What the research is telling us is that often a childhood history of trauma can predispose somebody to developing post-traumatic stress disorder. There may be underlying mental health issues that come out because of operational issues. I would say that operational stress injury is more encompassing. It allows for pre-existence of the condition or for a work-related cause. I think it's definitely more encompassing, and it's not a diagnosis.
It also allows for what a lot of the research is looking into right now—that some of this may not be a mental health injury. It may be a moral injury, and that's important to consider as well.