Doctors don't know what causes it, they have prescription to manage it, but not to cure it. Doctors don't know how to cure mental illness. Why I know? Cause I've experienced such. I've just had to fight against it. When I regained my mind after treatment, I read quite a few books. It turns out, every mental problem is a brain chemical disorder. And I started to try physical exercise, running 40 minutes a day, or dancing 1 hour a day. I tried for 1 year I started to feel much better, like Paul said the inner peace. It's all because of the chemicals the brain secrets after long time exercises. I'm no longer on pills, I'm not good all the time, from time to time I can notice the abnormal mood, and I try to manage it on my own. I also take antioxidants, and green tea. Hope my experience can be useful.