Editor’s note: This article originally appeared on rodalewellness.com.

If you find yourself chasing that enviable, happy feeling that appears at the end of a workout, you’re not alone. The runner’s high, seems to magically materialize at the end of your route, makes you smile, makes you more cheerful, and is one of the best byproducts of any run. 

For years, it’s been said that the high is a result of an endorphin release that eventually leads to this happy-go-lucky boost.

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But not anymore. According to a new study, published in the Proceedings of the National Academy of Sciences, a runner’s “high” could be the result of a different substance: endocannabinoids. Translation: Your body’s own version of cannabis. 

“A class of chemicals your body produces, endocannabinoids, is related to cannabis, the active ingredient in marijuana,” writes Dr. Jeff Brown, who is not affiliated with the study, in his book, The Runner’s Brain. “Scientists believe the endocannabinoid anandamide has an especially potent ability to lift mood, dull pain, and dilate the blood vessels and bronchial tubes in the lungs. When your brain and body cells release enough of these happiness molecules, you get the rush of good feelings that lead to the runner’s high.” 

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In their research, scientists from the Central Institute of Mental Health at the University of Heidelberg placed mice on running wheels and discovered that after their runs, they were less anxious, and thus happier. Enter the runner’s high. 

When the scientists blocked the animals’ endocannabinoid system, it turns out the mice were just as anxious at the end of their run as they were at the start. Turns out endorphins are not the end-all-be-all of the happy feeling, and that the runner’s high you experience could in fact be, well, a marijuana-like high. 

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“Whatever the reason, a runner’s high is like the ultimate form of dissociation and association rolled into a single brainwave; you feel no pain, yet you are one with your body,“ Brown writes. ”It’s almost as if your brain has decided that hard physical labor is the best thing that has ever happened to it. This is incentive for you not only to keep running this time around, but also to come back again real soon for more of those magical feelings.”