Lonely people feel more pain - friends help you create natural painkillers, research finds

An Oxford University study found friendship had an effect on the body, reducing stress and depression while boosting levels of the brain chemical endorphin which is stronger than morphine.

They also discovered that those who exercise or have high stress levels have fewer friends meaning they might get their endorphin 'hit' that way.

The study warned our modern isolating lifestyles with cyber friends rather than meeting up face to face could affect how our bodies cope.

It had set out to explore whether differences in a person's neurobiology explained why some had more friends and family than others.

Doctoral student Katerina Johnson in the University's Department of Experimental Psychology said: "I was particularly interested in a chemical in the brain called endorphin.

"Endorphins are part of our pain and pleasure circuitry - they're our body's natural painkillers and also give us feelings of pleasure.

"Previous studies have suggested that endorphins promote social bonding in both humans and other animals.

"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.

"To test this theory, we relied on the fact that endorphin has a powerful pain-killing effect - stronger even than morphine."

The study published in the journal Scientific Reports used pain tolerance as a way to assess the brain's endorphin activity.

It proved the theory that those with friends had a higher pain tolerance.

Ms Johnson added: "These results are also interesting because recent research suggests that the endorphin system may be disrupted in psychological disorders such as depression.

"This may be part of the reason why depressed people often suffer from a lack of pleasure and become socially withdrawn."

Yet she noted both fitter people and those with high stress levels tended to have smaller social networks.

She explained: "It may simply be a question of time - individuals that spend more time exercising have less time to see their friends.

"However, there may be a more interesting explanation - since both physical and social activities promote endorphin release, perhaps some people use exercise as an alternative means to get their 'endorphin rush' rather than socialising.

"The finding relating to stress may indicate that larger social networks help people to manage stress better, or it may be that stress or its causes mean people have less time for social activity, shrinking their network.

"Studies suggest that the quantity and quality of our social relationships affect our physical and mental health and may even be a factor determining how long we live.

"Therefore, understanding why individuals have different social networks sizes and the possible neurobiological mechanisms involved is an important research topic.

"As a species, we've evolved to thrive in a rich social environment but in this digital era, deficiencies in our social interactions may be one of the overlooked factors contributing to the declining health of our modern society."