The Runner’s High: What’s Really Going On in Your Brain

Rebecca Brown
Oct 27
4 min read

If you’ve ever finished a run and felt that wave of calm, clarity, or quiet joy wash over you — congratulations, you’ve met the runner’s high.

It’s that almost meditative state where your legs are moving, your mind feels clear, and for once, everything just flows.

But what’s really behind it?

The Old Story: Endorphins

For decades, we were told that the runner’s high came from endorphins, the body’s natural opioids. And while they do help reduce pain and make exercise feel less gruelling, here’s the catch — endorphins are too large to cross the blood–brain barrier.

That means while they act on receptors in your body (helping block pain signals), they don’t reach your brain’s emotional centres to cause that euphoric feeling.

So endorphins aren’t the whole story.

The Runner's High: Endorphins aren't the whole story. Image by Wix

The Real Star: Endocannabinoids

The modern explanation points to your body’s endocannabinoid system — the same system targeted by cannabis, but built naturally into your brain and body.

The two key players are:

Anandamide (AEA) — nicknamed the “bliss molecule” (from the Sanskrit ananda, meaning joy).
2-Arachidonoylglycerol (2-AG) — a similar molecule that supports pain regulation and reward signalling.

These are lipid-based neurotransmitters — small, fat-soluble compounds that can cross the blood–brain barrier easily and activate the brain’s CB1 receptors, which are densely packed in areas linked to mood, motivation, and emotion (like the amygdala, hippocampus, and prefrontal cortex).

When you exercise, your neurons and muscle cells release these endocannabinoids into the bloodstream, where they:

Reduce anxiety and stress by dampening overactive neural circuits.
Increase dopamine release in reward pathways, enhancing motivation and pleasure.
Reduce pain sensitivity through both spinal and brain mechanisms.
Contribute to that calm, “zoned in” feeling by balancing sympathetic and parasympathetic activity.

What the Science Says

The evidence from humans

A 2023 review by Siebers and colleagues pulled together every human trial measuring endocannabinoids before and after exercise — 21 studies in total.

Here’s what they found:

After acute exercise (typically 30–60 minutes of running or cycling), 82% of studies reported a significant rise in anandamide (AEA).
This increase was consistently linked to improvements in mood and reductions in anxiety.
2-AG, on the other hand, showed mixed results — roughly half of studies found increases, half didn’t.

Importantly, studies using moderate to moderately high intensity (around 70–85% of max heart rate) showed the strongest AEA response, and effects were seen even after just one session.

When participants trained regularly over time, their resting endocannabinoid levels dropped slightly, suggesting the system adapts — kind of like how your muscles or cardiovascular system adapt to training.

The outdoor experiment

A more recent study by Weiermair et al. (2024) took the research outside the lab — literally. Sixteen runners completed a 60-minute outdoor run, and the results were striking:

Both anandamide and 2-AG levels increased significantly after the run.
Mood scores jumped from an average of 6/10 before to over 9/10 after.
Women showed greater increases in anandamide than men.
Younger and less frequent runners had larger 2-AG spikes — suggesting that your endocannabinoid system might respond more dramatically when it’s not constantly stimulated by training.

In short: running outdoors, at a steady but challenging pace, reliably lights up your body’s own endocannabinoid system — producing measurable biochemical changes that align with that “high” feeling.

Inside Your Brain: How It All Connects

When anandamide and 2-AG flood the brain, they activate CB1 receptors, which modulate neurotransmitter release. Think of it as your brain turning down the volume on stress and turning up the channels for reward and calm.

In the amygdala, CB1 activation reduces fear and anxiety.
In the nucleus accumbens, it enhances dopamine — your motivation and reward centre.
In the hippocampus, it influences memory and emotional regulation.
In the prefrontal cortex, it supports that sense of mental clarity and focus.

Together, these effects produce what we call “runner’s high”: a unique mix of reduced pain, decreased anxiety, and a quiet, euphoric calm.

What Triggers It Best?

Research suggests you’re most likely to hit that blissful state when you: 🏃‍♀️ Exercise continuously for 30–60 minutes 💓 Stay at a moderate to moderately high intensity (where you can still talk, but not easily) 🌞 Get outdoors — sunlight and natural environments boost mood-regulating neurochemistry 🧘‍♀️ Find your rhythm — repetitive, rhythmic movements (running, cycling, swimming) encourage “flow state”

It’s less about going faster or harder, and more about sustained, rhythmic effort that gets you into that sweet physiological zone.

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References:

Siebers, M., Biedermann, S. V., & Fuss, J. (2023). Do Endocannabinoids Cause the Runner's High? Evidence and Open Questions. The Neuroscientist : a review journal bringing neurobiology, neurology and psychiatry, 29(3), 352–369. https://doi.org/10.1177/10738584211069981

Weiermair, T., Svehlikova, E., Boulgaropoulos, B., Magnes, C., & Eberl, A. (2024). Investigating Runner’s High: Changes in Mood and Endocannabinoid Concentrations after a 60 min Outdoor Run Considering Sex, Running Frequency, and Age. Sports, 12(9), 232. https://doi.org/10.3390/sports12090232