There have been some interesting articles that have studied the effect of both stress and loneliness and the changes they induce to our biology:
http://her2support.org/vbulletin/sho...eferrerid=1173
http://her2support.org/vbulletin/sho...eferrerid=1173
I don't think the absence of a positive attitude per se affects survival, but I do think that anything that induces an inflammatory response in the body runs counter to it.
Hopeful