Creativity and the psyche

While I was flipping the satellite channels to get rid of a spell of boredom, I stumbled upon a guest who was speaking about the relation between creativity and forms of mental handicapping. His words, style and enthusiasm attracted me to follow the program. He re-iterated a simple idea, which I heard about before, that many of the geniuses who produced many artifacts and masterpieces of music, literature, poetry or plastic arts were in the matter of fact, psychologically unstable and even were considered by some as insane. Some people said once that arts arise from madness! Is this idea always true to take for granted? Is the connection between the creativity and the psychic troubles solid enough and reproducible under laboratory circumstances, to find the true scientific evidence of its existence? Or is the case we are talking about merely coincidental, and variable. I read a lot about the relation between creative people and melancholy or psychic depression. Many artists were afflicted by a degree of neurosis, many times in their life. I think I have to read more about this phenomenon.