Usually, it's obvious when a person is mentally fucked up - cannot function, forgets things easy, cannot concentrate for more than 5 minutes, gets very aggressive without a sufficient reasons, etc. It's probably very important for the industry how this is calibrated and who gets legally paid for what. Sure we can say that that such person is not sick because of semantics.
However, I think it’s important to keep unstable and dangerous people off the street, no matter how scientific community will call it and separate them from those who can function if they take some sort of a pill. It’s like Bermuda triangle. Some say planes are missing there because they are abducted by aliens and others because of very explainable natural phenomena. As for me I don’t really care, but I will try to stay away from this region in either case.