Lots of times mental disorders only manifest/compound in the 20s.
I knew a guy who was fairly normal for the entire time I knew him, until he had a massive schizophrenic break in his mid 20s and went completely off the rails.
My half sister is schizophrenic so I know all too well about that. I think she was either 22 or 23 before she started having her delusions. I’m 21 now and every day I fear that it’ll happen to me eventually.