Employers are technically not allowed to discriminate on those grounds, but they can always say some bullshit corporatespeak like “we found another candidate more suitable for the position” and there's no way you can prove them wrong. I hate my factory job that I only got through my sister (lovely nepotism) and that has nothing to do with my degree I am passionate about, but I've been turned down more times than I can count.
But the courts determining disability eligibility don't care if your job makes you want to kill yourself. And they want to make you beg for years and years in court for it, even if it was the legal system that gave you the scarlet letter branding you a “psycho” in the first place.
When you're mentally ill, employers find any reason not to hire you, and the courts find any reason not to give you disability benefits.