I don't know if there is much empirical evidence that shows the effectiveness of some of these animals, especially with equine therapy. I haven't seen that, but I haven't done a ton of research on it. As I said, I'm more on the employment side of the equation; I'm not a mental health expert by any means.
I do think that it's a part of the positive transition experience for a lot of veterans who are suffering from combat and operational stress. Who hasn't ever seen a puppy make someone feel better? It is a positive thing in the transition.
More importantly, we need to be addressing other major issues when veterans are transitioning, such as unemployment, substance abuse, family challenges, and so on. If we can't prevent those things, then we'll never be able to prevent more chronic mental health issues.