I’ve just found an interesting letter to the British Journal of Psychiatry by A. J. McBride who noted the high level of mental illness in professional comedians.
Perhaps most well-known is the British comedian Spike Milligan who suffered from bipolar disorder and was frequently admitted to hospital.
In fact, a ward at the Maudsley Hospital in London, where he was admitted at least once, was opened by Spike. A plaque still commemorates the occasion.
The letter in the BJP was a comment on an earlier paper that noted the exceptionally high level of mental illness among jazz musicians.