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Friendship can have a surprising number of positive effects on health, scientists have found—maintaining friendships can decrease your risk for dementia and heart disease, can keep you fit (if they’re fit, too), and can even extend your life. Now researchers might have discovered another positive effect: friends can make pain hurt less, according to a study published today in Scientific Reports.

The researchers suspect that endorphins are the reason for the connection. “Endorphins are involved in both pain and pleasure circuitry,” Katerina Johnson, one of the study authors, tells Popular Science. You probably know that your body releases endorphins when you do exercise—those chemicals are fitting into the same receptors in the brain as morphine does, blocking any feelings of pain or discomfort the physical exertion would have caused.

There’s a theory that friendship can do the same thing. It’s called the brain opioid theory of social attachment. “Being attached to other individuals is so important to our survival—being close to our parents, close to our offspring, collaborating to find food,” Johnson says. So it makes sense that our bodies would want to reward us for good social interaction (and make us feel bad when we’re not getting enough of it).

The researchers used pain tolerance as a proxy measurement for the amount of endorphins that the body produces. In the study, the researchers analyzed data from 100 participants. Each of the participants reported their basic information (like age and sex) and completed a survey about their two innermost circles of friends: the people they contacted once per week, and the people they contacted once per month. The participants were then asked to do a wall sit—squat against a wall with legs at a 90 degree angle—for as long as they could stand it.

After adjusting for different fitness levels, the researchers found that people with a larger network of friends could do the wall sit for longer, which the researchers interpreted to mean that they had a higher pain tolerance and more endorphins. The result was strongest for people who had a larger second circle of friends (people they contacted once per month). And, interestingly, people who were more fit or more stressed had smaller circles of friends, possibly because they were getting their endorphins from other sources in their lives or they might also be busier and simply don’t have the time to maintain so many friendships.

The researchers believe this could shed light on the relationship between endorphins and mental illnesses like depression, which can increase antisocial behavior. And the researchers still don’t know how adaptable the endorphins system is to social changes, especially in adulthood when the brain is less plastic.

“It’s interesting, perhaps by enhancing our social health and feeling of connectedness to others, we might better be primed to deal with pain,” Johnson says. “But at the moment there is a lot more research required to understand what’s involved.”