For nearly fifty years, there was a tidy story about why exercise feels good. You run, your body floods with endorphins, you feel euphoric. The phrase “endorphin rush” lives in pop culture the way “sugar high” does, repeated so often it became fact.
It is mostly wrong.
The science has shifted significantly over the last decade, and the molecule getting most of the credit now isn’t an endorphin at all. It is an endocannabinoid, a compound your body produces on its own, structurally similar to the active compounds in the cannabis plant, that acts on the same receptors.
That is worth sitting with. Your body makes its own cannabis-like molecules. And one of them is largely responsible for the most famous feel-good moment in athletics.
This is the first piece in a series exploring how endocannabinoids relate to the other chemical messengers in your body, the ones you have probably heard of, like dopamine, oxytocin, and serotonin. Understanding these comparisons is the clearest way to understand why the endocannabinoid system matters, and why cannabis, as a plant, has the relationship to human physiology that it does.
We are starting with endorphins because the two systems are so often confused, and because untangling them tells a story that has been quietly rewriting itself in the scientific literature.
What Endorphins Actually Are
Endorphins are peptides (short chains of amino acids) produced primarily in the pituitary gland and the hypothalamus. The name is a contraction of “endogenous morphine,” and that is exactly what they are: morphine-like molecules your body makes itself.
They were discovered in the 1970s, when researchers were trying to figure out why opioid drugs like morphine and heroin worked so well in the brain. The answer was that the brain already had receptors specifically shaped to receive these kinds of molecules, which meant the body must produce something natural to fit them. That something turned out to be a family of compounds now called endogenous opioids, of which endorphins are one type. The others include enkephalins, dynorphins, and nociceptin.
When endorphins bind to opioid receptors (mainly the μ-opioid receptor), they produce powerful pain relief. Beta-endorphin, the most studied of the group, is roughly 18 to 33 times more potent than morphine on a molecule-for-molecule basis. Endorphins are released in response to pain, stress, intense exercise, laughter, certain foods, and physical intimacy. They are a core part of how your body regulates pain and reinforces behaviors that aid survival.
What Endocannabinoids Actually Are
Endocannabinoids are lipid-based molecules (fats, essentially) that your body produces on demand throughout the central and peripheral nervous systems. The two most studied are anandamide (often abbreviated AEA, and named after the Sanskrit word ananda, meaning bliss) and 2-arachidonoylglycerol (2-AG).
They were discovered in the 1990s, decades after endorphins, and the discovery happened in reverse. Scientists had already identified delta-9-tetrahydrocannabinol (THC) as the active compound in cannabis. They then found cannabinoid receptors in the human body. Then they went looking for what those receptors were supposed to be receiving and found anandamide. The plant compound came first in human understanding, but evolutionarily, the system inside us came first by hundreds of millions of years.
Endocannabinoids bind to two main receptors, CB1 and CB2. CB1 receptors are densely packed in the brain and central nervous system and influence mood, memory, pain perception, appetite, and stress response. CB2 receptors are concentrated in the immune system and peripheral tissues and play a major role in inflammation regulation.
The entire system, including receptors, the molecules that bind to them, and the enzymes that build and break them down, is called the endocannabinoid system, or ECS. The ECS is found in nearly every vertebrate species on Earth. It is roughly 600 million years old. Your dog has one. So does a goldfish.
Its job, broadly, is homeostasis – keeping your body’s internal systems in balance.
Where the Two Systems Genuinely Overlap
Endorphins and endocannabinoids are not the same thing, but they do share territory.
Both are released during exercise. Both contribute to pain relief. Both are involved in reward and the regulation of mood. Both can produce something that feels like euphoria under the right conditions. And both, for years, were grouped under the same loose pop-science umbrella of “feel-good chemicals.”
There is also evidence the two systems are functionally linked. Research from Kelli Koltyn et al. found that blocking opioid receptors with naloxone affects how the body produces anandamide during exercise, suggesting the two systems are talking to each other in ways researchers are still mapping.
So this is not a story of one being right and the other being wrong. It is a story of misattribution. The popular narrative gave endorphins credit for a job that endocannabinoids do most of.
The Runner’s High: A Case Study in Bad Assumptions
Here is where the comparison gets specific.
The runner’s high, that ephemeral wave of euphoria, reduced anxiety, and pain dulling that long-distance runners describe, has been credited to endorphins since the 1970s. It made intuitive sense. Exercise raises blood endorphin levels. Higher endorphins should mean a better mood. Case closed.
Except for one major problem: endorphins cannot cross the blood-brain barrier.
The blood-brain barrier is the body’s filtration system between circulating blood and the brain itself. It is highly selective. And endorphins are large, water-soluble molecules that are simply too bulky to pass through. Which means even when your blood is flooded with endorphins after a hard run, they’re not actually getting into your brain in any meaningful quantity.
Researchers started questioning this in the 1980s, but the alternative wasn’t clear until much later. The breakthrough came from a team led by Johannes Fuss at the University Medical Center Hamburg-Eppendorf. In a 2015 study published in Proceedings of the National Academy of Sciences, his group showed that mice given drugs that block opioid receptors still experienced the calming, pain-reducing effects of running. But mice given drugs that block cannabinoid receptors, or mice genetically engineered to lack those receptors entirely, did not. The runner’s high disappeared.
A 2021 follow-up study in humans, published in Psychoneuroendocrinology, confirmed the pattern. Runners given naltrexone, which blocks opioid receptors, still experienced the euphoria and reduced anxiety of running. The endorphin pathway was not required.
What is required is anandamide. Unlike endorphins, anandamide is fat-soluble and it crosses the blood-brain barrier easily. And it rises sharply during sustained aerobic exercise. A 2022 meta-analysis at Wayne State University found this effect was consistent across running, swimming, weightlifting, and other forms of exercise, and across populations with and without preexisting health conditions.
This is a substantial reframe of something most people thought was settled. The runner’s high is not an endorphin rush. It’s an endocannabinoid response. Your body is, in essence, dosing itself with its own cannabis-like compound every time you push through a long run.
Where Endorphins and Endocannabinoids Genuinely Differ
So if both rise during exercise, what’s actually distinct between them?
Chemistry. Endorphins are peptides or chains of amino acids. Endocannabinoids are lipids or fatty molecules. This difference is what determines whether each can cross the blood-brain barrier, which in turn determines whether they can act centrally in the brain or only in peripheral tissues.
Receptors. Endorphins act on opioid receptors (mu, delta, kappa). Endocannabinoids act on cannabinoid receptors (CB1, CB2). These are entirely different receptor families with different downstream effects.
Production. Endorphins are stored in vesicles and released when needed. Endocannabinoids are not stored at all, rather they are synthesized on demand from membrane lipids, used, and then quickly broken down by enzymes. This makes the endocannabinoid system far more responsive and localized than the opioid system.
Scope. The opioid system is heavily focused on pain, reward, and stress responses. The endocannabinoid system has a much broader portfolio: pain, mood, appetite, sleep, immune function, memory, body temperature, inflammation, reproduction, and more. The ECS is one of the most far-reaching regulatory systems in the human body, which is part of why its dysfunction has been linked to such a wide range of conditions.
Plant analogues. This is where the comparison becomes especially interesting for anyone curious about plant medicine. The opioid system has a plant analogue too, opium poppies produce morphine, which binds the same receptors endorphins do. The cannabis plant produces phytocannabinoids such as THC, CBD, CBG, and others that bind, modulate, or otherwise influence the same receptors that anandamide and 2-AG do.
In both cases, a plant happens to produce compounds structurally close enough to one of our own signaling molecules that our bodies respond to them. With opioids, the consequences of that overlap have been well-documented for centuries; therapeutic when used carefully, dangerous when not. With cannabis, the research is much younger, and the safety profile is dramatically different, but the underlying mechanism is the same: a plant compound interacting with a receptor system that already exists inside us, doing a job it was already doing before the plant was ever encountered.
Why This Matters
The reason this comparison is worth understanding is not to dismiss endorphins. They are a real, important part of how the body manages pain and reward. The reason is that the public conversation has historically been lopsided. We talk about endorphins constantly. We talk about endocannabinoids almost never, unless we are specifically talking about cannabis.
This is a gap worth closing, because the endocannabinoid system is not a cannabis-related curiosity. It is one of the body’s primary regulatory systems. It is active right now, in everyone reading this, whether or not they have ever encountered the cannabis plant. It is involved in nearly every major physiological process you have.
And it is one of the systems most directly modulated by phytocannabinoids, the compounds produced by cannabis. That is not a coincidence in the sense of cosmic intent. It is a coincidence in the sense of evolutionary convergence: a plant happened to produce molecules close enough to our own endogenous ligands that our receptors recognize them. That convergence is the entire reason cannabis has the effects on humans that it does.
When people ask why cannabis seems to help so many different conditions such as pain, anxiety, sleep, appetite, inflammation, seizures, mood disorders the answer is not that cannabis is some kind of cure-all. The answer is that the endocannabinoid system regulates so many different conditions, and cannabis interacts with that system. It is the breadth of the ECS, not the breadth of the plant, that explains the range.
A Note on What This Series Will Cover
This is part one. Future pieces in this series will explore how endocannabinoids relate to other chemical messengers your body produces – oxytocin and bonding, dopamine and reward, serotonin and mood, GABA and anxiety. Each comparison shows a different angle on the same underlying truth: your body has a sophisticated network of internal signaling systems, and the endocannabinoid system is one of the most important, and least talked about, among them.
If you want to go deeper now, Realm of Caring’s Research Library has more than 800 peer-reviewed studies on cannabinoids and human health, and our care team takes calls from anywhere in the world at no cost. If you have questions about your own endocannabinoid system, or how cannabis might fit into your care, that is what we are here for.
