It's no secret that rejection hurts. So it's a good thing our brains have a system in place that acts as a social "painkiller," according to a new study.


Researchers from the University of Michigan Medical School found that the brain's mu-opioid receptor system -- which is already known to release opioid chemicals in response to physical pain -- also releases opioids in response to social rejection.


"This is the first study to peer into the human brain to show that the opioid system is activated during social rejection[1] ," study researcher David T. Hsu, Ph.D., a research assistant professor of psychiatry at the university, said in a statement. "In general, opioids have been known to be released during social distress and isolation in animals, but where this occurs in the human brain has not been shown until now."


The findings, which are published in the journal Molecular Psychiatry[2] , are based on brain imaging conducted on 18 adult study participants. The participants were set up in a faux online-dating scenario, where they looked at pictures and read fictitious profiles of other adults, and then selected who they found most romantically desirable. The participants were all aware that the profiles and photos were fake.


Then, researchers put the study participants in a PET scanner to conduct brain imaging. While the participants were lying in the scanner, they were told that the person they thought was attractive didn't like them back. Researchers found a release of opioid chemicals in the brain, particularly in the brain regions linked with physical pain (the amygdala, midline thalamus, periaqueductal gray and ventral striatum).


There also seemed to be a link between the resiliency of the participant and the response by the opioid systems. People who scored higher on a resiliency trait test seemed to "be capable of more opioid release during social rejection, especially in the amygdala," Hsu noted. "This suggests that opioid release in this structure during social rejection may be protective or adaptive."


Interestingly, opioids were also released in the brain when participants were told that a person they liked liked them back, highlighting opioids' dual role in both decreasing pain and increasing pleasure.



Social rejection[3] has been shown in past research to actually be bad for health. A study in the journal Clinical Psychological Science, published last year, showed that social stressors could negatively affect the immune system[4] .


And a 2011 study also from University of Michigan researchers showed that pain from social rejection and physical pain[5] "hurt" similarly in the brain.



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  • Friends Get You Moving


    Research presented in 2012 found that something you might expect more from your mother -- nagging -- can actually work when it's coming from a pal who's pushing you to move more.

    In fact, the least active interviewees in this particular survey said they <a href="http://www.sciencedaily.com/releases/2012/04/120418134852.htm" target="_hplink">needed and even <em>appreciated</em> a nudge</a> now and then from friends.

    And working out with a friend has the added benefit of keeping you committed to your workout plan. There's no rolling over to hit the snooze button on that a.m. run if someone is waiting for you to show up!

    <em>Flickr photo by <a href="http://www.flickr.com/photos/geishaboy500/272639168/" target="_hplink">geishaboy500</a></em>




  • Friends Keep You Relaxed


    There's some truth behind friendship clichés like "a shoulder to cry on." In the face of great stress, talking with and leaning on friends really can help you get through troublesome times.

    A 2011 study found that among students, <a href="http://www.sciencedaily.com/releases/2011/10/111026091229.htm" target="_hplink">friendships helped reduce some of the stress of being bullied</a> or excluded at school.

    Women in particular may be predisposed to the calming benefits of friendship. Researchers found that <a href="http://www.sfgate.com/opinion/article/Fight-stress-with-friends-2858415.php" target="_hplink">females release the hormone oxytocin when stressed</a>, which encourages "tend and befriend" behavior, rather than the "fight or flight" reaction often observed in men, the <em>San Francisco Chronicle</em> reported. This encourages women to chat with their friends when stressed, and the chatting itself spurs the release of <em>more</em> oxytocin, which can have a calming effect.

    <em>Flickr photo by <a href="http://www.flickr.com/photos/epsos/4933098878/" target="_hplink">epSos.de</a></em>




  • Friends Help You Live Longer


    It's not quite as simple as connecting with friends and, poof, you're guaranteed to live to 100. But there <em>is</em> a significant body of research linking strong social ties to a longer lifespan.

    Australian research found that <a href="http://jech.bmj.com/content/59/7/574.abstract?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=friends&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&sortspec=date&resourcetype=HWCIT" target="_hplink">older adults with more friends were 22 percent less likely to die</a> during a 10-year study than their peers with fewer friends.

    And in a recent analysis of 148 studies, researchers found that people with stronger relationships had a <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1000316" target="_hplink">50 percent greater chance of survival</a>.

    <em>Flickr photo by <a href="http://www.flickr.com/photos/gribanov/" target="_hplink">egor.gribanov</a></em>




  • Friends Boost Cancer Survival Rates


    While friendships may help you live longer in any situation, social ties have also been linked specifically to overcoming cancer.

    A small 2005 study observed 61 women with advanced ovarian cancer. <a href="http://onlinelibrary.wiley.com/doi/10.1002/cncr.21147/abstract" target="_hplink">Higher levels of interleukin 6</a>, a protein marker for a more aggressive form of the disease, were found in the women with the weakest social bonds.

    An older study followed 86 women with metastatic breast cancer for a year and found that the women who participated in a weekly support group <a href="http://www.ncbi.nlm.nih.gov/pubmed/2571815" target="_hplink">lived twice as long</a>.




  • Friends Lower Heart Disease Risk


    Perhaps because of their relaxation powers, friends are also good for the heart. A 2005 analysis of social support theories found that weak social ties could <a href="http://www.ncbi.nlm.nih.gov/pubmed/16314591" target="_hplink"><em>double</em> heart disease risk</a>.

    The link between social support and a healthy heart is even stronger for men who make one very special social tie official. <a href="http://www.webmd.com/balance/news/20041108/social-ties-guard-against-heart-disease" target="_hplink">Married men</a> seem to experience a particular boost in heart health, WebMD reported.

    Stronger social ties in general seem to lower blood pressure, which helps the heart.

    <em>Flickr photo by <a href="http://www.flickr.com/photos/brentgambrell/4415887276/" target="_hplink">Brent Gambrell</a></em>