For years people have been under the impression that “runner’s high”—the feeling of euphoria you experience at the end of a workout—is caused by a release of endorphins. However, a study published in the Proceedings of the National Academy of Sciences indicates it is actually a product of endocannabinoids, not endorphins.
Dr. Jeff Brown writes in his book The Runner’s Brain, “Scientists believe the endocannabinoid anandamide has an especially potent ability to lift mood, dull pain, and dilate the blood vessels and bronchial tubes in the lungs. When your brain and body cells release enough of these happiness molecules, you get the rush of good feelings that lead to the runner’s high.”
How did scientists figure out that endorphins aren’t actually responsible for “runner’s high”? Endorphins are large molecules, so they are unable to pass through the blood-brain barrier—this means that endorphins can relieve muscle pain, but they cannot affect the brain in any way. Anytime you feel “high” it originates in your brain, therefore there is no way that a release of endorphins could cause “runner’s high”. Endocannabinoids are small enough to pass through the blood-brain barrier, allowing them to interact with the CB1 and CB2 receptors of our endocannabinoid system. Scientists have discovered in recent years that exercise in humans (and animals) increases the level of endocannabinoids in the bloodstream, which leads them to believe that endocannabinoids are what cause you to feel so happy and relaxed after you exercise.
A study done by the Central Institute of Mental Health at the University of Heidelberg medical school in Mannheim, Germany confirmed these findings—scientists took a group of mice and tested their anxiety levels, then placed them on a running wheel. These mice ended up having less anxiety post-run than when they were tested before running. A second group of mice were given drugs to block their endocannabinoid system and these mice were actually more anxious after their run and less tolerant of pain. A third group had their response to endorphins blocked (but their endocannabinoid system unchanged) and these mice experienced similar responses to the first group with increased relaxation and decreased anxiety. This proves that endocannabinoids, not endorphins, are responsible for “runner’s high”. So if you enjoy the relief you feel after a run, both mentally and physically, you might consider using medical cannabis at the beginning of your exercise regimen to lift your mood, dull your pain and dilate your blood vessels and bronchial tubes in your lungs.