This Happened to Me!
It was not in a mental hospital but on a college campus (pretty close).
I began dating a professor who was brilliant, charming, and quirky.
He became progressively more quirky, assuming that we would get married and start having children right away, giving me a washing machine as a gift for no reason, and distributing memos about how wonderful I was to everyone he knew. I asked him what was going on, and he said he had stopped taking his "medication" because it turned him into a robot and he wanted to live for once.
While I tried to figure out what to do, the course of events made the decision for me: he no longer recognized me, he threatened his students with an antique dagger, he began to dress as a medieval rabbi, he was relieved of his duties and his mother came to collect him. I never saw him again, and never got to answer his proposal of marriage. The year was 1989.
"Have I sent you my protocol sheet?"