I have been told that a psychosis has to have medication. It will not just go away on it's own. It continues to worsen until hospitalization maybe necessary. That's my experience.
I have forgotten to take my thyroid meds, and given myself a psychosis. It's called myexedema madness. He may have another health condition driving the psychosis. It's good to get ontop of it, check his electrolytes and consult with a doctor.