For many runners, especially more experienced ones, the illustrious runner’s high is a powerful experience—a euphoric flow state that helps athletes power through high-mileage runs, easing anxiety and melting away stress. Conventional wisdom says endorphins, a class of pain-killing chemicals naturally produced by the body, are the cause. But emerging research is upending that theory. Turns out a runner’s high is caused by endocannabinoids, naturally occurring cannabis-like compounds that are released during enjoyable activities, like having an orgasm, according to a new study.

 

 

Previous studies found when mice developed a similar high from running, endorphins didn’t play a role, but cannabinoid receptors did. Researchers suspected similar mechanisms might be involved in humans, too.

“Those previous findings were based on a mixture of behavioral, pharmacological, and molecular genetics studies,” Johannes Fuss, the lead author of the new study, told Runner’s World. “But obviously, we couldn’t study the effects of euphoric feelings in mice. So, we repeated the experiment with humans.”

For this new study, the researchers recruited 63 experienced runners, both men and women, and focused on two clear markers of the typical runner’s high: euphoria and reduced anxiety, The New York Times reports. Half of the participants were given naloxone, a drug that blocks opioids like endorphins, then all of them ran on a treadmill for 45 minutes at a moderate intensity.

Afterward, the researchers analyzed the participants’ blood and made a key discovery: All of them showed elevated levels of endocannabinoids. In addition, most of them reported experiencing a high, including the runners who were dosed with naloxone. In other words, cutting out endorphins had no significant effect, and runners were able to enter their flow state as usual.

It’s strong evidence that the body’s naturally occurring cannabis-like chemicals are the real cause of the runner’s high. In addition, endorphins can’t penetrate the blood-brain barrier, which makes them an unlikely candidate for triggering the altered mental state that runners experience. Endocannabinoids, on the other hand, can cross into the brain, and they play a major role in the body’s signaling mechanisms. The data makes a strong case: If there’s one kind of chemical that can make running double-digit mileage feel as good as sex, it’s probably endocannabinoids.

So who needs weed? The easiest way to get high might be to head out for a run.

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