Parkinson has been considered as a factor to Robin Williams depression but not actually the cause. According to an article on TMZ, Robin Williams was devastated when his last show #TheCrazyOnes on CBS was cancelled that contributed a lot into deep depression that led to his death.
#TheCrazyOnes is an American Sitcom he starred with Sarah Michelle Gellar from September 2013 to April 2014. It was cancelled after 1 season only. Sources who told TMZ that Robin Williams considered the cancellation as a personal failure and it hit him really hard.
I did watch all the episodes of #TheCrazyOnes and I find it intelligently funny and relevant. The show was all about the advertising world evoking realism and campaigns.
I was sad when #TheCrazyOnes wasn't renewed what more if that was announced to the person who was the face of the show. #RIPRobinWilliams
To those of you who wasn't able to watch the show, here is a preview: