I suffered from rapid cycling manic depression, I believe it was partly induced from a very hard hit from a soft ball (gave me a concussion).
I went on lithium for 18 months, though I probably only needed for 6 or so, and was completely cured. It's been that way for 7 years now, no meds at all.
Lithium acts through several different channels and mechanisms, but after some reading I believe it reset my brain and I was fine after that.
I never ever want to experience what I did back then, hardly anyone can imagine how painful it got for me. The hardest part of psychotropic drugs is the lag of 1-4 weeks for effects to become apparent, if then.
The body is what moves you around but your mind is the ultimate governor and determine how and where you end up. That's why most homeless people are either very ill or crazy.
