A new study carried out by researchers from the University of Heidelberg in Germany and published in the Proceedings of the National Academy of Sciences (PNAS) states that a runner’s high is caused by endocannabinoids rather than endorphins in the system.

Runners feel high after some time exercising or running and witness an experience often associated with people taking marijuana or cannabis; researchers earlier thought that the excessive release of endorphins while running activities cause this feeling, but they can now prove that it is caused by endocannabinoid compounds in the body.


Endorphins produce feelings similar to those produced by morphine, but endorphins are only natural compounds produced in the body and help relieve pains. More endorphin is produced by the body when athletes or runners experience muscle stretching or tearing during intense exercises.

The German researchers conducted three experiments on lab mice to establish the actual chemical responsible for the runner’s high experience.

“If you place a running wheel in a mouse’s cage, it will run voluntarily, covering great distances of about 10 km/day over twelve hours each day,” said Dr. Johannes Fuss, lead author of the study. “They’re really motivated to run; there are strong biological processes motivating these mice to run in running wheels, therefore they’re a good model to study why humans are motivated to do exercise.”

The researchers divided the lab mice into two groups, making one group to run on wheels placed in their cages while the second group was exempted from this exercise. The researchers then measured high levels of endocannabinoids in the running group, indicating that the exercise makes the mice insensitive to both pain and anxiety.

Some drugs were then administered the drugs to block either endorphins or endocannabinoids while the mice ran, yet the sensitivity of the mice to pain and anxiety reduced, but this is not the case in the other group.

In a third test, researchers reared mice that were genetically bred to lack cannabinoid receptors in their brain. These mice ran on wheels in their cages on the first day but later grew tired of running and would not run again a few days after, making researchers to conclude that endocannabinoids have been helping them run before.

The researchers explained that a runner’s high is the sense of well-being that athletes experience after a prolonged exercise. Scientists had for decades thought endorphin release produced the feeling of goodness, but this new study shows endocannabinoids actually cause it.