How can having a sense of community affect one's physical health?

No easy answer: "Pop" wisdom is that involvement with community makes people healthy, but it may simply be that people who are sicker cannot get out or socialize so much. Especially, it can be cruel to pressure an invalid to try to do things they know they cannot do well. Despite a half century of talk, there are no hard findings or known mechanisms by which positivity alters the course of any illness.