Not sure about “alot” but definitely you’re right in the case of Hillary and Obama.
I'd agree that mental illness is caused by a number of factors including: drug abuse, poor life choices, irrational expectations and coping strategies, flirtation with the dark side of the moral spectrum, (i.e. folks that practice and believe in the occult), faith in nothing beyond themselves, (i.e. atheists, agnostics), etc.
I'd guess that the vast majority of mentally ill folks followed a very flawed yellow brick road. It's probably a small minority of the mentally ill that are seriously ill in spite of good life choices and a "normal" environment.
For those who are politically crazy, changing your political affiliation is simple and easy. Check the right box anytime you choose. You'll still have irrational thoughts and impulses from time to time. A little talk radio, Fox News, and an honest days work will have you mentally fit in no time. :-)