I have heard a lot of times about the therapeutic effect of animals, not just with dolphins. Dogs are used in old people's home to help residents having an interest: they have to take care of the dog, and this task helps them to keep active and busy. I have recently heard about similar experiences in prisons, too. There's another animal with an entirely own therapeutic discipline, horses. They can help specially mentally handicapped people, who establish a relation with the animal through walks that definitely helps patients.
And, of course, we have always heard about dolphins' special personality and their relation with humans. In fact, I think that a few years ago there were some kind of dolphintherapy center in the known location of Cadaques, at the Costa Brava, where people could swim with dolphins. But, fortunately or not, they close it because it hadn't the necessary documentation, so I guess that they released the dolphins.