I'm not scientist, but I learned in school that whenever there's a correlation, it helps me to stop and question: chicken or egg?
Maybe some people have become depressed because they have been trying to mold themselves into a mono life.
Maybe some people are lonely, and that leads to depression, and poly brings more people around them to love.
I've also heard that many people with bi-polar disorder are very creative, and poly is another creative way of looking at life and love.
I posted this quickly because I have to run, but I just had to throw something in there to subscribe to the thread, haha! Looking forward to further discussion on this topic.
Formerly married to Sundance
Boyfriend -- Butch Cassidy