By Lily Yang,
Many long-distance runners are driven by their pursuit of the “runner’s high,” which is described to be a feeling of euphoria and invincibility reached after covering lengthy distances. Exercise in general is known to stimulate the release of a cocktail of mood-boosting neurotransmitters, such as endorphins, dopamine, norepinephrine, and serotonin (1). The most widespread and popular theory regarding the chemical basis of the runner’s high originates from a study in the 1980s that investigated endorphins and subsequent mood changes during long-distance running (2). The study proposed that the runner’s high is a result of the prolonged release of endorphins, which are natural opioids produced by the body. It was believed that these exercise-induced endorphins would bind to the same opioid receptors as morphine and heroin, consequently producing similar feelings of euphoria as these drugs (2).
However, this common theory has since been called into question. Although it is true that blood levels of endorphins are higher after exercise, endorphins have large bulky chemical structures that prevent them from passing through the blood-brain barrier to produce an effect on the brain (3). Instead, recent studies have investigated a different molecule as being primarily responsible for producing the runner’s high – endocannabinoids. Similar to how an endorphin is the naturally produced version of morphine in the body, an endocannabinoid is the body’s version of cannabis. Since endocannabinoids are small molecules, they can easily diffuse through the blood-brain barrier to act on cannabinoid brain receptors, the same ones that THC in marijuana binds to, and activate the brain’s reward pathway (4).
In a study conducted on mice, a specific endocannabinoid called anandamide was investigated. The mice were divided into a non-running control group and a running group that ran for several kilometers per day. When compared to the control group, the running group displayed higher levels of circulating endocannabinoids in their blood, exhibited decreased anxious behavior, and had higher pain tolerances (4). Other studies conducted on humans and dogs also found significantly higher blood levels of endocannabinoids in the subjects after they had completed a treadmill exercise session (5).
Interestingly, not all exercise is equal in producing endocannabinoids. A study that was conducted on humans running on a treadmill at four different intensity levels found that the level of endocannabinoids released during exercise was dependent on exercise intensity. Surprisingly, very high intensity exercise (as well as very low intensity) yielded no significant increases in endocannabinoids post-exercise, whereas moderate intensity exercise yielded much higher levels of endocannabinoids (6). This could also explain why long-distance runners who tend to run at a moderate, steady pace are more likely to report experiencing the runner’s high, as opposed to high-intensity sprinters.
The basis of the runner’s high doesn’t have to be simply limited to chemicals binding to receptors. Being able to push oneself to run long distances can instill a gratifying sense of self-discipline and accomplishment that pushes people to pursue and love running. Furthermore, running can build confidence, relieve stress, as well as decrease one’s risk for developing depression and anxiety (7). No matter what the cause is, running offers a plethora of mental benefits for both the short and long term.
- Berkeley Wellness. “Chasing Runner’s High?”. Berkeley Wellness University of California. 21 May 2013. http://www.berkeleywellness.com/fitness/exercise/article/chasing-runners-high
- Markoff, R.A., Ryan, P., Young, T. “Endorphins and mood changes in long-distance running.” Med Sci Sports Exerc. 14, no.1 (1982):11-5. https://www.ncbi.nlm.nih.gov/pubmed/7070250
- Kotler, Ryan. “Runner’s high Revisited”. Psychology Today. 20 May 2008. https://www.psychologytoday.com/ca/blog/the-playing-field/200805/runners-high-revisited
- Fuss, J. et al. “A runner’s high depends on cannabinoid receptors in mice.” 112, no.42 (2015): 13105-13108. http://www.pnas.org/content/112/42/13105
- Raichlen, D.A. et al. “Wired to run: exercise-induced endocannabinoid signaling in humans and cursorial mammals with implications for the ‘runner’s high’.” Eur J Appl Physiol. 113 (2014): 869-875. https://www.raichlen.arizona.edu/DavePDF/RaichlenEtAl2013.pdf
- Raichlen, D.A. et al. “Exercise-induced endocannabinoid signaling is modulated by intensity.” Eur J Appl Physiol. 113, no. 4 (2015): 869-75. https://www.ncbi.nlm.nih.gov/pubmed/22990628
- Taylor, C.B., James F. Sallis, Richard Needle. “The relation of physical activity and exercise to mental health.” Public Health Rep. 100, no.2 (1985): 195-202. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1424736/