Do you know what he was depressed about?
Not specifically, but I believe he was diagnosed as bi-polar, like Jonathan Winters and other brilliant comedians, so the swings from euphoria to depression were part of the cycle of that illness. I know he had a coke problem back in the 70s/80s, and went thru detox/rehab. It was in the SF papers, as was his numerous stints in exclusive Malibu/Carmel clinics.
When he was on, he was *on*...
https://www.youtube.com/watch?v=M9FMrjDasBk