Mental illness aside, Hollywood can really strain the minds of people since the real issue is survival. Fighting for parts, fighting for recognition, fighting for press. It can wear you down and basically throw your mind if you don’t have iron focus and the ability to handle uncertainty.
Do you think that's a driving factor behind the fact that so many actors are so utterly divorced from reality? It does not make sense for people who live in mansions and have unimaginable wealth to advocate to destroy the society and government that made their success possible, yet they do that all the time.