Congratulations, you played yourself.
Unless it's not psychological illness but physical one, I mean if his braincells are actually damaged the halucinations probably will stay no matter what he do until the cell is recovered.here's an idea, bro (if you live)
ask the hallucination to help you with your work or creative endeavors. maybe it'll be better than chatgpt
tho I suppose if he had that kind of thought process, he wouldn't be having a persistent hallucination in the first place. it'd probably naturally dissipate once you start testing the extents of what it can do