Perhaps this experiment was never tried by scientists, but it was tried by a playwright, in The Ruling Class by Peter Barnes. The movie adaptation should be available somehow, and I recommend it. The recently late Peter O'Toole plays the 14th Earl of Gurney, who believes himself to be Jesus, God of Love. His family, horrified and embarrassed at his mental illness, will have no truck with all that "love" nonsense, and hire a psychiatrist to "cure" him. The doctor brings in another delusional patient, who believes himself to be the angry Old Testament vengeful God. The treatment has its desired effect! The 14th Earl no longer believes himself to be Jesus. Instead, he believes himself to be Jack the Ripper, who goes out and commits murder. This, thank goodness, is perfectly all right with his family, who accept him unto their bosom once more.