http://www.sciencedaily.com/releases/2006/08/060814133621.htm
This is interesting, although kind of what you'd expect if you've ever used e.g. counter-conditioning. I also can't help wondering about the implications for those who maintain that e.g. depression is a chemical problem that requires drugs rather than counselling. But to be fair, it's something I know very little about so don't have any right to be opinionated!