Stopping the progression is a pretty big step. You do adapt to the disease if the progression is slow such as
in the young onset forms. I suspect that many don't quite realize that not all adaptations are favorable.
For instance, when your dopamine comes in pill form, or is moderated by something in pill form you can
have a period of mania after you take the pills, and a suicidal depression that lasts for a few minutes before
going to sleep. After years of this one tends to get a little scrambled up upstairs.
Psychosis is one of those little "whoopsie" features of jumpstarting dopamine conversion with tyrosine or
carbodopa, and all the rest. It hit about 30% who take relatively high amounts. As for the percentage of people
who are convinced that people are out to get them, or some other effect comprable to hitting that caffeine
too hard, who can say.
And then there are the extreme ends, the ones who want to kill the fundies so they can get their stem cells
and go back to being functional again, or who are looking down on hitting stage three and possibly looking
at just a little bit of payback. Worst case maybe you get the chair before you hit stage four, or wait, maybe
that would be the upside. ;)