Many people have felt that strange mix of mental clarity, calm, and wellbeing after running, cycling, or doing intense exercise. For decades it was believed that this sensation, known as the runner's high, was the result of the release of endorphins.
Today we know the story is much more interesting. Various studies suggest that a significant part of that experience depends on endocannabinoids, molecules the body itself produces naturally and that activate the endocannabinoid system.
One of them, called anandamide, rises in the blood after certain types of exercise and can cross the blood-brain barrier, allowing it to influence the brain directly. There it takes part in processes related to mood, anxiety, pain perception, and the sense of wellbeing.
That doesn't mean the body produces cannabis. It means something even more fascinating: the body produces its own cannabinoids. And perhaps one of the most natural ways to activate them is to move.
Explore in depth
If you'd like a deeper understanding of the biological mechanisms, scientific evidence, and current research, continue to the full version of the article.
The science behind this
For years we blamed endorphins
The classic explanation said that exercise releases endorphins, known as the body's "natural painkillers." It makes sense: endorphins reduce pain perception and increase tolerance to effort. However, there was a problem. Endorphins are large molecules and cross the blood-brain barrier with difficulty, so they don't fully explain the intense sense of wellbeing and euphoria many people describe during exercise.
Then anandamide appeared
When researchers began measuring endocannabinoid levels after exercise, they found a striking pattern. Following moderate-intensity aerobic activities, concentrations of anandamide, one of the body's main endocannabinoids, increased.
Anandamide even carries the nickname "the bliss molecule," derived from the Sanskrit word ananda, meaning "happiness" or "bliss." Unlike endorphins, anandamide can indeed reach the brain and interact with CB1 receptors, contributing to changes in mood, anxiety, and pain perception.
The body doesn't produce THC
Here it's important to make a distinction. The body doesn't produce THC or CBD. It produces endocannabinoids, such as:
- Anandamide (AEA).
- 2-arachidonoylglycerol (2-AG).
These molecules serve similar functions because they interact with the same biological system. In other words, the body has its own version of the cannabinoid language, though it uses molecules different from those in the cannabis plant.
Why does exercise increase them?
Exercise is a challenge for the body. It increases energy demand, changes body temperature, speeds up the heart, and activates multiple physiological systems. In response, the endocannabinoid system takes part by helping maintain homeostasis. During that process, endocannabinoid levels can rise, favoring effects such as:
- A greater sense of wellbeing.
- Lower pain perception.
- Reduced anxiety.
- A feeling of calm.
- Greater ease in entering a state of focus, or flow.
Not everyone experiences a runner's high
If you've ever run and thought, "well, I never felt that euphoria…", you're not alone. The response depends on multiple factors:
- Intensity of the exercise.
- Duration.
- Level of training.
- Genetics.
- Physiological state.
- The workings of the endocannabinoid system.
In addition, the available systematic review found that although most studies observed increases in endocannabinoids after acute exercise, there is still no definitive proof that they alone explain the whole experience of the runner's high in humans. It's likely the result of the interaction between several neurochemical systems.
An orchestra, not an instrument
Today most researchers no longer explain the runner's high through a single molecule. The most recent evidence proposes that a genuine neurochemical orchestra is involved. Endocannabinoids seem to coordinate much of the experience, while other substances, such as endorphins, dopamine, serotonin, and BDNF, also contribute from different roles.
What we know today
The evidence supports fairly solidly that:
- Moderate aerobic exercise usually increases circulating endocannabinoid levels.
- Anandamide can cross the blood-brain barrier and influence processes related to wellbeing.
- Endocannabinoids play an important role in reducing the anxiety and pain perception associated with exercise.
- The runner's high likely depends on the interaction between several neurochemical systems, not on a single molecule.
What is still being researched
- What type, duration, and intensity of exercise produce the greatest release of endocannabinoids.
- Why some people experience the runner's high easily and others almost never.
- The exact contribution of each neurotransmitter and neuromodulator to this experience.
- How to harness these mechanisms to improve mental health and wellbeing.
Conclusion
For a long time we thought that the wellbeing after exercise was a story about endorphins. Current science invites us to tell it another way. There is more and more evidence that the endocannabinoid system plays a central role in that sense of calm, clarity, and wellbeing that can appear after running, cycling, or doing aerobic exercise.
The body doesn't make cannabis. But it does produce its own cannabinoids. And perhaps that's one of the most surprising demonstrations that wellbeing doesn't always come from the outside. Sometimes, it begins with a walk, a bike ride… or the first kilometer of a run.
Further reading
- Fuss J, et al. A runner's high depends on cannabinoid receptors in mice. Translational Psychiatry.
- Siebers M, et al. Do Endocannabinoids Cause the Runner's High? Evidence and Open Questions. The Neuroscientist.
- Meeusen R, et al. Exercise, brain and cognition: neurochemical mechanisms. PMC Review.
- The Conversation. The runner's high may result from molecules called cannabinoids: the body's own version of THC and CBD.
