What medication is Michael Phelps using for his mental illness?

My sister is mentally retarded just like Michael Phelps. She has Geiner/Stolskontz disorder (sp?) which I think is the same type of retardation Phelps has. Does anyone know what he's on? Is it possible he uses marijuana for medical reasons? I'd really like to know because if marijuana could help my sister it would be great. It's so sad to see that vacant look in her eyes like Phelps has. I know that there's a good person in there, but she doesn't do anything except ride her bike around the block. She's also using Haldol and Elavil. Is Phelps using these same drugs? It seems his illness is handled slightly better than my sisters and I'd appreciate any little improvement.