Several comedians were/are mentally ill.
Sam Kineson. Robyn Williams. Bill Cosby. Richard Pryor. Jim Carey. Freddie PPrince. Andy Kaufman.
And numerous more were not, including but not limited to Fred Allen, Jack Benny, Shelley Berman, Sid Caesar (whose issues were substance abuse, not mental illness), Totie Fields, Groucho Marx, Henry Morgan, Bob Newhart, and Mort Sahl.