The death of Chris Cornell

A few days ago we lost one of the most talendet vocalists of our times. Chris Cornell was a lead singer of two well-known american bands: Soundgarden and Audioslave. For the first time I came across his music time when I was around twelve. He comitted suicide at the age of 52.
I often wonder what makes people kill themselves. Is it the grey everyday life they can't stand anymore? Or is it because of more complex emotions they can't manage with? It's easy to tell "I am currently feeling suicidal" but there must be some deep and dark dimention of this feeling that makes people loose interest in their lives. Unfortunately, for many who reach that point there is no return. What an overwhelming feeling it must be when you loose every little spark of hope. Seriously, what does it feel not to wish for sunshine anymore?