Recently scientists have evidences suggesting that some of the same neural machinery recruited in the experience of pain may also be associated with social, verbal and virtual separation or rejection.
in the ones who are lonely resembling to that of the one who are under physical pain. And the perception is also by the same area of brain.
The study seems to indicate that the average person is wired to need social acceptance.
This explains why people wear something just because everyone else does, why it stings so much to be the last person picked for a game, and why people start knitting groups. It indicates that we have an inherent need for the company of others.