After running or working out, people experience a number of sensations. This is known as the runner’s high, and studies suggest it is produced because of a cannabinoid found in our own brain.

“Run, Forest! Run!” Remember that scene from that awesome and timeless movie? Forest escaping from those bullies in bikes, rushing to the end-zone or crossing the entire country with a beard while the crowd followed him. “I just felt like running”, he said in that unforgettable accent of his. After those metal supports came off his legs, he never stopped running.

Well, the truth is that Forest Gump was high as a kite on endocannabinoids. And if you are a regular runner, you probably have experienced the same high as Forest. Psychologically, and according to WebMD, runners experience euphoria, a feeling of being invincible, a reduced state of pain or discomfort and even loss in sense of time while running.

This concept is known as runner’s high. Biologically speaking, running sets in motion a lot of chemical reactions that give that sensation of being unstoppable. For a long time, scientists thought endorphins were responsible for that high. However, studies found that there is a direct correlation between intense aerobic activity and the endocannabinoid system.

What is Runner’s High?

Forest just sitting in his dock, looking at the horizon with his Bubba Gump hat laying in his lap. Then, something clicks in that mind of his. He gets up slowly and starts running. “That day, for no particular reason, I decided to go for a run. And for no particular reason, I just kept on going”. He ran all across his beloved Alabama and continued all the way to the west coast.

During the last decade, running has become one of the most popular activities in the United States. According to Bureau of Labor Statistics, in 2003, only 15.9% of people 15 and older participated in some form of exercise. That number grew up to 20% in 2015. And if you don’t believe statistics, just take a look at your street or your nearest park in the morning. You are going to see a whole army of people with an armbands, headphones and running shoes. And just like Forest, when people start running, they just keep on going.

But, if you start to think about it, you have to ask the question: Why do people like Forest and why are your neighbors so into running? We can answer that. And, no. The answer is not Jenny!


For decades, scientists have tried to figure out why exercise becomes so addictive for some people like Forest Gump. Some dare to say that it is as addictive as any other drug. Actually, it is not that far from the truth. During the 80’s, some studies concluded that there was a direct link between endorphins and running. Endorphins, in a very superficial definition, are the opioids that our bodies produce naturally.

Endorphins interact with several receptors in the brain that reduce perception of pain. Also, endorphins produce a positive feeling in our bodies. Endorphins can also be released during other physical activities, like sex. So when Jenny got into Forest’s bed, he also got high on endorphins. Naughty Forest.

But let us go back to running. A study published during early 1984 made a review on the evidence on exercise and endorphins. Among other findings, it concluded that there was significant evidence that endorphins “depress ventilation and play a role in ventilatory regulation”. This means that high levels of endorphins can change the perception of fatigue.

Furthermore, in 2009 a study explained how addictive exercise can become. Scientists concluded that, when taken to extremes, exercise can “develop into an addictive-like behavior”. Mice were submitted to exercise on a running wheel. They got so addicted to it that they showed a dependency similar to that observed in morphine dependant patients. Rats who went through high intensity running showed very severe withdrawal symptoms. There where even cases of mice that preferred running over eating to the point of even dying.

Recently, a new study came up. It suggested that endorphins were not the ones in charge of creating runner’s high. Another chemical compound created by our bodies came up: anandamide.

What is Anandamide?

Forest Gump was first released on June 23, 1994. Two years before that, halfway around the world, a couple of scientist discovered a chemical compound created in our brain. This chemical compound was proof that every human body produces its own cannabinoid. On March 24, 1992, Lumír Hanus, a Czech chemist, and William Devane, an American pharmacologist, isolated for the first time a cannabinoid produced in the human brain. They called it anandamide.

Hanus and Devane were working in the Hebrew University of Jerusalem. They were part of a team lead by Dr. Raphael Mechoulam, world’s leading scientist on cannabis.

Hanus and Devane called this new molecule Anandamide because of the Sanskrit word “ananda”, which means “joy, bliss or happiness”. Anandamide is also known as the “bliss molecule”. It is the mimetic twin of THC, another cannabinoid. Unlike anandamide, it is found in the cannabis plant and produces psychoactive effects. But what they do have in common is that they both activate CB1 and CB2 receptors in our brains. And most importantly, anandamide produces psychological and physical effects like euphoria and pain relief.

Although it is hard to believe director Robert Zemeckis knew anything about anandamide, his lead character is full of it throughout the movie. At the beginning, when we said that Forest was high on cannabinoids, we really meant it. It turns out that when Forest was running or playing ping pong like his life depended on it, anandamide was all over his brain. And remember that part when he was in Vietnam, running through the jungle trying to save Bubba and Lieutenant Dan, he screamed “something bit me!”? Well, maybe the reason why Forest didn’t feel that much pain when that bullet reached his buttucks was because of anandamide flowing through his brain.

Endocannabinoid System, Anandamide and Runner’s High

Because of the discovery of anandamide, scientists started to consider that endorphins were not the reason for the runner’s high. When you start jogging, playing ping pong or running all across the Vietnamese jungle, endorphins are not the reason for that feeling of euphoria. Anandamide is.

Twenty three years after Hanus and Devane isolated anandamide for the first time, German scientists made the link between the endocannabinoid system, anandamide and runner’s high. They proved, among other things, that endorphins had nothing to do with the “high”.

Goodbye endorphins, Hello Anandamide!

These German researchers observed in the study that endorphins can’t pass the blood-brain barrier. However, they also found high levels of an endocannabinoid called anandamide. Contrarily, anandamide could travel from blood to brain. They also found high levels of anandamide in people’s blood after running. Anandamide has two important effects that are directly involved with runner’s high: analgesic and anti anxiety effects.

The researchers proved this with mice that were acquainted to exercise in a running wheel. They divided that group into two: one group would continue to run for 5 hours per day, while the other one remained without exercise.

After this, scientists submitted the mice to different tests to measure and analyze anxiety, pain reception and sedation. Their findings showed that two of the endocannabinoid system receptors played a major role in runner’s high. When anandamide interacts with CB1 receptors, it inhibits anxiety. While CB1 and CB2 receptors both have a response on pain reduction.

To get back to Forest, maybe that’s why he was so calm in the middle of a war and how he managed to keep on running even though he was shot in the buttock.

Other scientists, this time from the Arizona’s School of Anthropology, measured the endocannabinoid system responses in humans, dogs and ferrets, before and after treadmill exercise. They wanted to compare non-cursorial mammals (mammals that don’t have limbs suitable for running) such as ferrets with cursorial mammals, like dogs and humans like Forest.

Their study showed that humans and dogs show an increase signaling of the Endocannabinoid System after exercise. On the contrary, ferrets don’t experience much change in their endocannabinoid system after running. These findings can explain why “humans and other cursorial mammals habitually engage in aerobic exercise despite the higher associated energy costs and injury risks”.

Forest Gump is high on anandamide

Running made Forest very happy. It got him from playing football to winning a congressional medal of honor. He crossed the whole country and, most importantly, made his mama really proud. And while he did all of that, his endocannabinoid system was working as hard as he did. Every time Forest runs, anandamide levels start rising in his brain, nervous system and endocannabinoid system.

It is not endorphins but cannabinoids the ones that provide that runner’s high. Studies prove that anandamide, our very own and self-produced cannabinoid, gives Forest and the millions of runners in the world that bliss, that joy and that high after exercising.