My experience with therapy dogs
I have read some of these posts and I felt the need to share my experience with therapy dogs in wilderness settings, which has been somewhat, well, pretty much negative. I ran outdoor programs for a university a few years ago, when a girl came in and asked if she could sign up and bring her dog. When I said, "no, we don't allow pets," she claimed that it was a "service dog." I asked what service it performed and she told me that I wasn't allowed to ask her that because she was protected by the American's with disabilties Act. After some discussion with the program's coordinator, we decided to allow the dog to go. 6 1/2 hour van ride to summit Wheeler peak in Nevada, and many students complaining as the dog laid across three laps in the packed van and everything/one covered in hair, the dog nearly didn't make the summit, and as nice as the dog was, it was just a pain in the butt.
A few weeks passed and the girl came in again wanting to sign up for a Zion Narrows backpack with the dog. We told her absolutely not, it was not safe for the dog... She argued that she could sue the University if we did not allow the dog. At the time we had no idea what service the "service dog performed" but it was apparent that this girl was not mentally sound. After pleading our case to our recreation director, we apprehensively allowed the dog on the trip.
The dog nearly drown twice in the Narrows, no joke. The dog literally limped out of the canyon the second day with bleeding paws. It had swam rapids, chased a deer far beyond our group, upset everyone, left poop all over the canyon (although our agreement was that she would stay with the dog and clean up after it), and in the end we just felt terrible for this dog and animosity toward this client. The dog performed no service. On the bus ride back to camp, a stranger asked the girl what service her dog performed and her response, was that it helped her with her emotional problems. I was livid.
The next trip was Havasupai. She came in, I told her the trip was full (it wasn't). She told me that she planned to get her own permit and lower her dog on ropes below Mooney Falls. What the hell!
The point of my story agrees with many of the other buzzards when I say, "those who are mentally unsound, or even teetering on the edge of unsound, have no business in backcountry setting with animals." I have guided many trips on rivers for "at-risk" youth and have seen nothing but success. However those trips are highly structured, highly staffed by trained and caring individuals, and no doubt, just would not be the same on a private trip. Don't just leave the dog behind, leave the friend behind. Good Luck!