The physical exertion of having a good belly laugh in the company of friends as opposed to a polite titter, exhausts us so much we produce protective endorphins that raise our pain threshold and make us feel good, according to a new international study led by Oxford University in the UK that was published online in Proceedings of the Royal Society B on Wednesday.

Lead author Professor Robin Dunbar, Head of the Institute of Social and Cultural Anthropology at the University of Oxford, and colleagues found that when we laugh properly, we exhale repeatedly without drawing breath, an involuntary mechanism that only appears to happen in humans (our great ape cousins breathe out when they laugh).

This physical effort leaves us exhausted and triggers the release of protective endorphins, one of the complex neuropeptide chemicals of the brain that regulate pain and promote feelings of well being.

The team found that watching just 15 minutes of comedy in the company of others increased the pain threshold by an average of about 10%.

It seems that laughing with others is more likely to produce this effect than laughing alone.

Dunbar told the media that they think it is the “bonding effects of the endorphin rush that explain why laughter plays such an important role in our social lives”.

“Very little research has been done into why we laugh and what role it plays in society,” he added, explaining that they used microphones to “record each of the participants and found that in a comedy show, they laughed for about a third of the time, and their pain tolerance rose as a consequence.”

The researchers suggest the fact only this type of laughter releases endorphins is because it probably evolved as a way of encouraging us to socialize with each other.

The endorphin “rush” appears to occur only when we have a good belly laugh (one that creases the eyes, as opposed to polite laughter that does not reach the eyes), and when we share it with others.

The researchers write that other studies have repeatedly shown that laughter is 30 times more likely to happen when we are with others than when we are alone.

The research that Dunbar and colleagues describe took more than 10 years. They conducted different experiments to find out what influenced pain threshold.

For instance, in one set of experiments they invited participants to watch excerpts of TV programs or live staged shows and measured their before and after pain thresholds. They used various methods to take the measurements, such as painful, strenuous quad workouts, ice-cold sleeves, and applying pressure with a blood pressure cuff.

The TV excerpts included clips from Mr Bean and Friends, which were contrasted with clips designed to elicit neutral responses, such as excerpts from factual programs such as how to play golf.

In another set of experiments the participants watched nature programs designed to elicit “feel-good” responses, but just like the factual programs, they did not raise the pain threshold. This is why the researchers concluded that it was laughter itself, by triggering endorphin release, that was important, not just the feel-good effect.

In a third set of experiments the researchers compared pain thresholds between participants who watched staged dramas with those who watched stand-up comedy at the Edinburgh Fringe Festival. This showed the raised pain threshold effect happened in real life too and not just in the lab.

In conclusion they write:

“We suggest that laughter, through an endorphin-mediated opiate effect, may play a crucial role in social bonding.”

The study reinforces other findings by Dunbar and his team that show social activity produces endorphins. For instance a study that Dunbar wrote about with co-author Dr Emma Cohen found that pain thresholds rose in members of a rowing team when they trained as a team but not when they trained as individuals.

There are also other studies that suggest social activities like performing music, dancing and religious rituals produce “euphoric” states through endorphin release.

Written by Catharine Paddock PhD