I think so. I have a colleague, Dr. Gordon Asmundson, who is currently running a study on exercise therapy as a component intervention for PTSD specifically. Exercise, generally speaking, is a really good thing, full stop, especially if it's being done appropriately.
That said, I think we need to be very careful to understand that exercise alone is not a panacea. It's not going to resolve everything but, full stop, is it a good idea to engage in exercise, and will it help with depression, mood in general, and mental health and anxiety? All of the evidence seems to suggest yes.