A social snub can deliver a seemingly painful blow. Now, it turns out that sting may be real. A gene linked with physical pain is also associated with a person's sensitivity to rejection, a new study finds.
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The discovery doesn't suggest that being chosen last for a pick-up ball game, say, will send you limping off the field. Rather, a rare form of the so-called mu-opioid receptor gene (OPRM1) is likely involved in the emotional aspect of physical pain — essentially, how much a person is bothered by a throbbing leg, for instance.
In the study, 122 participants indicated how much they agreed or disagreed with statements, such as "I am very sensitive to any signs that a person might not want to talk to me." Their saliva was also analyzed for OPRM1.
(People with a rare form of OPRM1 experience more physical pain than others.)
Then, the researchers used functional magnetic resonance imaging (fMRI) to scan the brains of 31 of the participants during a virtual ball-tossing game. Initially, each participant was included with two virtual players before being excluded when the virtual players stopped throwing the ball to them.
Individuals with the rare OPRM1 variant were more sensitive to social rejection. The mutant-gene carriers also showed more activity in brain regions linked with physical and social pain, including the dorsal anterior cingulate cortex and anterior insula.
Such social pain may have benefited our ancestors. "Because social connection is so important, feeling literally hurt by not having social connections may be an adaptive way to make sure we keep them," said study researcher Naomi Eisenberger of UCLA.
She added, "Over the course of evolution, the social attachment system — which ensures social connection — may have actually borrowed some of the mechanisms of the pain system to maintain social connections."
The research, which is published in the Aug. 14 online early edition of the Proceedings of the National Academy of Sciences, was funded by the National Institute of Mental Health, National Institute of Aging, and the Harry Frank Guggenheim Foundation.
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