I used to work with someone who had a pretty serious mental illness, remitting & recurring, but he was in denial about it. I can tell you about stress and burnout of those around him, who had to be ready to jump in when after about 6 weeks of full-time work (teaching & admin) during term time, he'd have a minor or a major breakdown. That university expected everyone simply to pick up his work, and because he was in denial and either said he wasn't ill, or demanded very unreasonable accommodations, they did nothing. I left - 3 years as HoD managing this person almost made me ill.
I know this sounds very ableist but I think there's a real problem about the way universities expect other staff to make up for disabled staff - in my experience, that is.