Researchers from Hungary found that study participants with a variant of a gene that has previously been associated with risk for psychosis (the T/T polymorphism of the neuregulin 1 gene) scored higher on two measures of creativity than participants who had the more common variants of this polymorphism. Szabolcs Kéri reported that participants with the T/T polymorphism of the neuregulin 1 gene had higher scores on the Creative Achievement Questionnaire (developed by yours truly and my colleagues) and also on divergent thinking tests (often used as a measure of trait creativity). None of the participants showed signs of psychosis. The author suggests that this variant of the gene may reduce cognitive inhibition, and thus have a positive impact on creativity by allowing more ideas to filter into conscious awareness. Previous research (including work from our lab) has indicated that both psychotics and highly creative individuals may exhibit cognitive disinhibition. (You can read more about how cognitive disinhibition affects creativity in Chapter 5 of my book, Your Creative Brain.)
Carson, S.H, Peterson, J.B., & Higgins, D. M. (2003). Decreased latent inhibition is associated with increased creative achievement in high-functioning individuals. Journal of Personality and Social Psychology, 85(3), 499-506.
Kéri, S. (2009). Genes for psychosis and creativity: A promoter polymorphism of the neuregulin 1 gene is related to creativity in people with high intellectual achievement. Psychological Science, 20(9), 1070-1073.