Having more friends may mean you also have a higher tolerance to pain, scientists from Oxford University claim. Neurobiological differences in our brains could indeed influence both our response to physical suffering and the way we socialise.

The research, published in Scientific Reports, focuses on the role of endorphins - chemicals released by the brain and associated with pain relief, euphoria or feelings of happiness. The scientists wanted to understand whether higher levels of endorphins could also be linked to having larger social networks.

Sociability and endorphins

Previous studies have suggested that endorphins promote social bonding and that people with higher endorphin signalling in their brain tend to feel more socially attached to others.

However, scientists say it is still unclear what causes this relationship. Is it that people are more sociable because their brain can produce more endorphins? Or rather, that people get higher endorphins levels when they interact with others, which make it easier for them to socialise the next time around?

"One theory, known as 'the brain opioid theory of social attachment', is that social interactions trigger positive emotions when endorphin binds to opioid receptors in the brain. This gives us that feel-good factor that we get from seeing our friends", explains lead author Katerina Johnson.

What is certain is that endorphins are involved both in pain (physical and social) and pleasure circuits of the brain. Whilst we know that social interactions help give us a feel-good sensation, Johnson's research shows that having a large social network is also linked to having a better tolerance to pain. "Endorphins can act as natural painkillers produced by the body", Johnson explains.

The "wall-sit" game

The study involved participants completing questionnaires about their social networks and answering questions about their personality and lifestyle. They were then asked to go through a physical task, squatting against a wall with knees at a 90° angle and a straight back. This is also known as "the wall-sit test". Even when allowing for individual differences in fitness levels, researchers found that people with larger networks of friends were, on average, able to stay longer in this position and tolerate the pain.

"More research needs to be dedicated to the endorphin system, but from what we know it is crucial to social interactions. Some studies have shown for example that if you block the endorphin system you appear to reduce people's feeling of social connection," Johnson concludes.

"The quantity and quality of our social relationships affect our physical and mental health, so understanding why individuals have different social networks sizes and the possible neurobiological mechanisms involved is an important research topic".