This Ted Talk by Andrew Solomon is very good. He describes very well what is going on inside a depressed persons mind. He says depression is living without vitality.
http://www.ted.com/talks/andrew_solo...ecret_we_share
I have battled depression for 30 years. With the help of a wonderful pyscologist and with the right combination of drugs, for the first time in my life my depression is under control. It's a disease, just like any other, where treatment is available. For me it was so hard to admit I need help and to become vunerable enough to actually do the psychological work. I had a close family member commit sucide after a lifetime of depression. I was going down that path as he was. It saddens me so much that my relative, Robin Williams and others did not have the opportunity to experience the correct treatment and to feel what it is really like to have vitality in life.