There is a correlation between mental disorders to the far right on the IQ bell curve (although many people argue IQ doesn't measure intelligence) and farther to the left on the bell curve. Basically, they are more likely farther from the middle.

On the right end, being gifted and having a learning disability, such as dyslexia, is called being twice exceptional. I'm not sure if the same term applies to mental illnesses and being gifted. However, there are many studies showing correlations between anxiety, ADHD, and dyslexia and giftedness. Also, in a relatively new book called Ungifted, the author shows a connection between bipolar and creativity as well as a higher chance of schizotypy traits in people with more creative jobs. There are tons of books in the library about this. Try looking up twice exceptional or a specific mental illness you're curious about.