Plato said that the muses gave us the arts not for "mindless pleasure" but "as an aid to bringing our soul-circuit, when it has got out of tune, into order and harmony with itself". It's no coincidence that Apollo is the god of both poetry and healing; nor that hospitals or health sanctuaries in ancient Greece were invariably situated next to theatres, most famously at Epidaurus, where dramatic performances were considered part of the cure. When Odysseus is wounded by a boar, his companions use incantations to stop the bleeding. And the Bible has the story of David calming Saul: "And it came to pass, when the evil spirit from God was upon Saul, David took a harp, and played with his hand: so Saul was refreshed, and was well, and the evil spirit departed from him."
Bibliotherapy, at the Guardian. Reminds me of a friend whose method for recovering from a painful breakup was to read all of Shakespeare. He was better halfway through.