Runner's High: Is It Really Endorphins? What the Research Says
💡 Key Summary
✅ A mood lift after a long run has been seen in human studies too
✅ The "it's all endorphins" story has weakened, and endocannabinoids are now a leading candidate
✅ Studies are small and conditions are narrow, so don't worry if you never feel it. Treat the good mood as a bonus
"Keep running and suddenly the effort fades and you feel great." You've heard that, right? But on most runs you just feel out of breath and wonder, "Where's my runner's high?" This guide is for runners who want to know whether the runner's high is real and what causes it, based on the research so far.
1. Is the Runner's High Real?
The runner's high is a loose name for the happy, calm, less-painful state that can follow a long run. The first direct look at the brain came in 2008. Researchers from the Technical University of Munich and the University of Bonn had 10 athletes run for 2 hours and compared PET brain scans before and after.
The scans used a tracer that competes with endorphins for the same spots. After the run, less tracer attached, especially in front-of-brain and limbic areas that handle emotion. The team read this as endorphins taking up those spots, and the more euphoric a runner felt, the less tracer attached.
| Study | Who | Key result |
|---|---|---|
| 2008 Munich/Bonn | 10 athletes | Brain endorphin sites changed after 2 h |
| 2015 PNAS | Mice | Cannabinoid receptors needed for less anxiety and pain |
| 2021 human trial | 63 runners | Blocking endorphins kept the mood effect |
Ten people is a small sample. A first study isn't the final answer!
2. Endorphins or Endocannabinoids?
Endorphins were long the star of the story. But endorphins are thought to cross from blood into the brain poorly, so doubts lingered. In a 2015 PNAS study in mice, a drug that blocks opioids like endorphins (naloxone) did not remove the lower anxiety and pain sensitivity after running.
Blocking cannabinoid receptors, though, reduced those effects. Anandamide, one of the body's own cannabinoid-like molecules, rose in the blood after running. A 2012 study found it rose after exercise in humans and dogs, but not in ferrets, a low-activity animal.
- Human study: in 2021, 63 people took an opioid blocker (naltrexone) or placebo, then did a 45-minute moderate treadmill run and a walk
- Result: running left people happier and less anxious than walking, with or without the blocker
- Blood: anandamide and another endocannabinoid, 2-AG, went up after running
📌 Note
These studies show endorphins aren't required, not that they do nothing. Endocannabinoids are a "leading candidate," not a confirmed cause.
3. When Does It Show Up, and Why Is It Fine If It Doesn't?
The conditions in these studies were fairly specific. Human work used a 2-hour run or a 45-minute moderate run, and participants exercised regularly. From the sources used here, we can't say whether a short run produces the same change.
These are also average results, so not everyone feels the same. The mouse researchers noted that euphoria can't be measured in mice. The lead of the 2012 study suggested that people with low activity levels may respond weakly and could build fitness first.
| Myth | A better way to see it |
|---|---|
| No high means I ran wrong | Study conditions were narrow |
| Endorphins are the proven cause | Newer work points elsewhere |
| Short runs don't work | These sources can't say |
⚠️ Caution
A post-run mood lift doesn't replace treatment for depression or anxiety. If low mood or anxiety lasts over 2 weeks, talk to a medical professional. Stop right away if you get chest pain, dizziness, or a cold sweat while running.
4. How to Run Without Chasing the Runner's High
The point isn't to "feel it." It's to go out and run. If you're too out of breath, you'll remember the struggle, not the joy. For finding a talk-friendly speed, see Easy Run Pace: How to Find Yours and the 80/20 Rule.
- Easy speed: if you could hum a tune, it's enough
- Note your mood: jot down one line after each run
- Low expectations: if it doesn't come, fine; if it does, bonus
If you feel great, your body rewarded you. If not, it was a rest-your-body day!
In the Wittiz app report, first check how many times you ran in the past month. Log the distance and pace of the days you felt good and you'll see what kind of run suits you. You can also spend the jelly you earn on dressing up Moongti.
Frequently Asked Questions (FAQ)
How long do you have to run to get a runner's high?
There's no set time. The studies here used a 2-hour run and a 45-minute moderate run, and we couldn't confirm what happens on shorter runs. Don't push to hit a number. Run at an easy pace.
Is the runner's high caused by endorphins?
That used to be the common view. But a 2021 human trial found the mood effect stayed even with endorphin signaling blocked, so endocannabinoids are now a leading candidate. Neither is confirmed.
If I never feel it, am I running wrong?
No. The studies are small, their conditions are narrow, and people feel things differently. Feeling a little refreshed afterward is enough.
Wrapping Up
The runner's high is probably real, but endorphins alone don't explain it. On days you don't feel it, your run still counts.
This week, run an easy 20 minutes and write one line about your mood afterward. Moongti will run right beside you!
Try it for yourself in the Wittiz app!
References
- Fuss J et al. (2015). A runner's high depends on cannabinoid receptors in mice. PNAS
- ScienceDaily (2008). Coverage of the runner's high PET study (Boecker H et al., Cerebral Cortex)
- ScienceDaily (2012). Coverage of the runner's high and exercise evolution study (Raichlen DA et al., J Exp Biol)
- ScienceBlog (2021). Coverage of the human naltrexone study (Siebers M et al., Psychoneuroendocrinology)
This article was written by the Wittiz team and includes app-related content. If you have symptoms of depression or anxiety, a medical condition, or feel chest pain or dizziness while running, please be sure to consult a medical professional.