There comes a moment during every run or long bout of exercise when the exhausted "Oh God, why am I doing this" feeling turns into a glorious sense of accomplished euphoria. This feeling is colloquially dubbed "runner's high" and is usually attributed to hormones called endorphins.
A new study published in PNAS has revealed, however, that endorphins aren't solely responsible for this feeling. A neurotransmitter called anandamide is released during exercise and it plays a big role in this running-induced happiness. There's an interesting twist, too: this neurotransmitter acts on the cannabinoid receptors that are also in use when getting high via marijuana.
"We thus show for the first time to our knowledge that cannabinoid receptors are crucial for main aspects of a runner's high," the authors wrote in the paper.
In addition to the feelings of happiness, this neurotransmitter also helps dull the sensation of pain, reduces anxiety and also acts like a sedative.
The researchers were able to make this claim after studying mice who exercised on a running wheel. These mice showed significantly higher levels of both anandamide and endorphins than those that were sedentary. The physically active mice were also shown to be more relaxed and have a reduced reaction to painful stimuli than the control group.
All in all, it appears that the brain perceives a runner's high similarly to getting high from pot in mice. There are a couple shortcomings to this study, however, as many of the effects of these chemicals are largely subjective, which makes it impossible to determine while studying mice.
More importantly, however, it provides a deeper understanding of what exactly is going on during runner's high and how exercise could be implemented into therapy for a number of ailments, including depression.