By
Stuart Wolpert
8/17/2009 AM
http://newsroom.ucla.edu/portal/ucla/a-genetic-link-between-pain-and-98593.aspx
Their study indicates that
variation in the mu-opioid receptor gene (OPRM1),
often associated with physical pain, is related to how much social pain a
person feels in response to social rejection. People
with a rare form of the gene are more sensitive to rejection and
experience more brain evidence of distress in response to rejection than those with
the more common form.
The
research was published Aug. 14 in the early online edition of
Proceedings of the National Academy of Sciences and will appear in the
print version in the coming weeks.
The findings give weight to
the common notion that rejection "hurts" by showing that a gene
regulating the body's most potent painkillers — mu-opioids — is
involved in socially painful experiences too, said study co-author Naomi Eisenberger, UCLA assistant professor of psychology
and director of UCLA's Social and Affective Neuroscience Laboratory.
In the study, researchers
collected saliva samples from 122 participants to assess which form of the
OPRM1 gene they had and then measured sensitivity to rejection in two ways. First, participants completed a survey that measured their
self-reported sensitivity to rejection. They were
asked, for example, how much they agreed or disagreed with statements like
"I am very sensitive to any signs that a person might not want to talk to
me."
Next, a subset of this group, 31
participants, was studied using functional magnetic resonance imaging (fMRI) at UCLA's
"What we found is that
individuals with the rare form of the OPRM1 gene, who were shown in previous
work to be more sensitive to physical pain, also reported higher levels of
rejection sensitivity and showed greater activity in social pain–related
regions of the brain — the dorsal anterior cingulate
cortex and anterior insula — in response to
being excluded," Eisenberger said.
The dorsal anterior cingulate cortex and anterior insula
are brain regions often associated with the distress of physical pain. Previous research by Eisenberger
and her colleagues has shown that these brain regions are also involved in the pain
of social rejection.
"Although it has long been
suggested that mu-opioids play a role in social pain
— and there are convincing animal models that show this — this is the
first human study to link this mu-opioid receptor
gene with social sensitivity in response to rejection," Eisenberger said.
"These findings suggest that
the feeling of being given the cold shoulder by a romantic interest or not
being picked for a schoolyard game of basketball may arise from the same
circuits that are quieted by morphine," said Baldwin Way, a UCLA
postdoctoral scholar and the lead author on the paper.
Eisenberger
argues that this overlap in the neurobiology of physical and social pain makes
good sense.
"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," she said. "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."
Shelley E. Taylor, UCLA
distinguished professor of psychology, is also a co-author on the paper.
The research was funded by a
National Institute of Mental Health (NIMH) postdoctoral fellowship, the
National Institute on Aging, the NIMH and the Harry
UCLA is