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Endocannabinoids Not Endorphins

I always thought that the chemicals that work magic in our brains post-exercise were endorphins, even though I was not clear what endorphins were. However, researchers are now looking at an alternative molecule as the cause of such relaxation and “runner’s high.” An article in “Canadian Running” Magazine explains this switch.

“Yes, endocannabinoids are the same chemicals that are mimicked by cannabis, which both alleviate pain and improve your mood. In fact, brain scientists often refer to endocannabinoids as the “don’t worry, be happy” chemical. Recent research has revealed that these compounds, instead of endorphins, are more likely the cause of the runner’s high because of their size. Endorphins are released into your bloodstream during exercise, but they’re too large to cross the blood-brain barrier, so they can’t cross over into your brain. Endocannabinoids, on the other hand, are small enough to cross over and act on specific receptors in your brain.”

Endocannabinoids (eCBs) are still little understood: “little is known under what circumstances eCBs are released during exercise in humans.”

Researchers will likely build on these initial studies and tell us more. But from now on, I will credit endocannabinoids instead of endorphins for why I feel better after exercise.

There is an additional open question for me: where do endorphins do their work? I will need to research that further.


Links to the Two Articles

The Science Behind the Runner’s High

in Canadian Running magazine, written by Brittany Hambleton on January 13, 2021

New Study Confirms Endorphins Aren’t the Cause of the Runners High

in Canadian Running magazine, written by Brittany Hambleton April 13, 2021

Additional Reading

For more detail, see the following research studies:

Exercise-induced euphoria and anxiolysis do not depend on endogenous opioids in humans.

in Psychoneuroendocrinology, Volume 126, April 2021 by Michael Siebers and Sarah V. Biedermann

Article Highlights

• Exercise-induced euphoria and anxiolysis are independent of direct occupancy of endogenous μ-opioid receptors binding.

• Running reduces anxiety levels in a human elevated plus-maze.

• Running stimulates the endocannabinoid system.

• Endocannabinoids are better candidates than endorphins to explain a runner's high in humans.


Do Endocannabinoids Cause the Runner’s High? Evidence and Open Questions

Neuroscientist Article first published online: January 26, 2022 by Michael Siebers, Sarah V. Biedermann, Johannes Fuss

Abstract: The runner’s high is an ephemeral feeling some humans experience during and after endurance exercise. Recent evidence in mice suggests that a runner’s high depends on the release of endocannabinoids (eCBs) during exercise. However, little is known under what circumstances eCBs are released during exercise in humans. This systematic review sampled all data from clinical trials in humans on eCB levels following exercise from the discovery of eCBs until April 20, 2021.