Is the idea of a 'sad clown' actually true?

Study finds that comedians are more prone to have 'high levels psychotic personality traits' 

A new recent study has found that that comedians may be more inclined to "high levels of psychotic personality traits". According to research published in the British journal of Psychiatry people with "unusual personal structure" with traits similar to bipolar is surreptitious to making people laugh. This was backed-up with statistical data gathered from 500 comedians who completed s questionnaire. However this may not be entirely reliable as the comedians may of faked their answered due to demand characteristics. 

There have been comedians who have openly reported their experiences with mental health, such as: Stephen Fry, David Walliams and Paul Merton, to name a few. 

Retired professor of experimental psychology at Oxford University, Gordon Claridge stated "Obviously not all comedians are like this, but the trend does seem these personality traits are more common. It is that idea of the sad clown". 

Stand up comedian Juliette Barton who has a history of tackling mental health problems responded, "These findings make sense to me. There is something about the solo comedy performers... quite a few I know have experience with mental health issues. If you do have issues, then comedy is often the way of getting you through." 

Logically it would make sense if comedians had a link with bipolar as comedy mimics the ability to combine "ideas or categories of thought to form new and original connections". The results of the questionnaire show that comedians scored pretty high on personality traits such as being unsociable, depressive as well as extrovert maniac traits. 

In conclusion I found these results quite shocking at first, however after giving it some thought it made more sense to me. It is difficult for me to believe that someone who is so happy/funny on stage may be suffering from depressive conditions.