Creativity and mental illness linked?

people who have "mental illness" ( I don't like that term) are usually more sensitive than the other people. it is called hypersensitiveness in France, I don't know if it's the same word in English? People who are hypersensitive are more creative and artistic than the other people. I believe it's something about left brain, but I'm very bad in sciences and I don't really remember ^^
So I think it's one of the explanations. There is obviously, like Nopurpose said, the fact we need more to give voice to our feelings, without talking.