That depends on the mental problem.
Are the effects of a toothache like the effects of a stroke?
There is a pretty wide range in mental health issues as to what the effects are, the duration, the cause, and the completeness of recovery.
PTSD (as an example) arises from unprocessed memory of a traumatic experience. Mild cases are completely recoverable, and relapses are unlikely.
Schizophrenia has a stress component and a genetic component. Treatment is often lifelong.
And those.just address completeness of recovery, not potential for violence.
The question as posed is so broad as to have no possible intellectual solution (other than to break it down. )
Those are interesting thoughts but I don’t see any connection to the question I asked.