The problem with that is it can make you "zoom in" on negative thoughts or insecurities, which might be dangerous and cause the patient to freak out. I've seen people freak out on LSD, which is generally much more powerful than psilocybin mushrooms. I've never seen anyone freak out on mushrooms, but I'd imagine that it could happen.
I guess it all depends on the patient and whether or not they want to try it. If they're dying and want to, let them. But for people with psychiatric disorders, it's probably not a good idea. I did acid when I was in my 20s and not as far gone as I am now. And music was a lot better back then, also.