There has been a lot of anecdotal evidence linking creativity and mental illness. This fascinating article "Neuropsychological evidence for dimensional schyzotypy: Implications for creativity and psychopathology" published by a team of researchers in the Journal for Research in Personality in 2oo4, establishes a link from a neurobiological perspective between creativity and psychopathology - schizotypal personality disorder in particular. The 'link' seems to be hemispheric asymmetry with a more pronounced right-hemispheric activity. Read the article here