When a person falls, processes in the brain allow for the release of natural opioids, which help ease some of the pain associated with the fall. But now, a new study finds that these same processes could activate when someone is rejected by a possible love interest, and that the strength of these processes is determined by a person’s resilience.

For a small group of participants, learning that they had been rejected by a potential love interest through a pseudo-online dating experiment caused opioids to be released from the mu-opioid receptor system of the brain, particularly in the ventral striatum, amygdala, midline thalamus, and periaqueductal gray. These areas are also associated with opioid release during physical pain. Those who scored higher for resiliency on personality tests also tended to release more opioids during rejection, signifying that these processes were meant to protect or adapt the participant from rejection, the researchers said.

“This is the first study to peer into the human brain to show that the opioid system is activated during social rejection,” David Hsu, PhD, lead author of the study and a research assistant professor of psychiatry at the University of Michigan, 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.”

For the study, researchers asked a group of 18 participants to look at photos and profiles of hundreds of potential love matches, and to indicate who they found attractive. The participants then underwent positron emission tomography (PET), which scanned their brain as they were told that the people they were interested in didn’t feel the same way about them.

Their brains instantly showed opioid release, with those more resilient releasing higher levels of the chemical. The researchers also found that those who released the most opioids in another part of the brain known as the pregenual cingulate cortex were the least likely to feel bad that they’d been rejected. They also found that opioids were released out of pleasure when participants discovered their love interest was also interested in them.

Perhaps the most surprising result of the study, however, was that these participants’ brains reacted in this way even when they were told beforehand that the dating profiles and rejection weren’t actually real.

Although the study measured rejection through romantic interest, the researchers say that the study’s findings could apply to depression and social anxiety research. “It is possible that those with depression or social anxiety are less capable of releasing opioids during times of social distress, and therefore do not recover as quickly or fully from a negative social experience. Similarly, these individuals may also have less opioid release during positive social interactions, and therefore may not gain as much from social support.”

For those who aren’t depressed, social rejection may not be the worst thing either. A 2012 study found that being rejected from groups of people could foster a sense of validation. For these people, an “independent self-concept” developed, and that led to more imaginative.

Source: Hsu D, Sanford B, Meyers K, et al. Response of the μ-opioid system to social rejection and acceptance. Molecular Psychiatry. 2013.