I knew someone like that in school and for him it was a demon issue. He was a normal student, its just that when he was alone he used to talk to two spirits which he said he was born with. Anyway, my advice to you is keep praying for your friend. I believe madness too is the work of demons and can be removed through prayer too. If you have other bible believing christians around you, get them to pray with you. We are more than conquerors, and have been equiped to overcome the enemy. God bless