New research credits molecules called endocannabinoids for causing the feeling of runner’s high, according to a study in mice published last week in the Proceedings of the National Academy of Sciences. According to the Washington Post, the sensation of euphoria brought on by endocannabinoids feels a lot like the high brought on by marijuana.

This contradicts the belief that the psychological benefits of aerobic exercise—including reduced anxiety and sensitivity to pain—are direct results of endorphins interacting with the central nervous system.

Researchers at the Central Institute of Mental Health of the University of Heidelberg in Germany came to their conclusion after observing the endocannabinoid systems in the brains of mice. The mice observed were more easygoing and less sensitive to pain after a few laps on an exercise wheel. These effects faded after the mice were given drugs that blocked their endocannabinoid system.

“Wheel running increases endocannabinoids and reduces both anxiety and sensation of pain in mice,” the researchers said in the study’s abstract.

While the new findings suggest that exercise can produce some of the same results as marijuana, it is still unclear whether marijuana can boost the results of exercise. There is anecdotal evidence that cannabis may act as an anti-inflammatory but has negative effects for athletes, including reduced motor skills and coordination.