M. Sibers, S.V. Biedermann, L. Bindila, B. Lutz, J. Fuss
Psychoneuroendocrinlogy, 126 (2021) 1015173: 1-7
It is deeply ingrained in current biological and health sciences education that the “runner’s high” is a function of increases in endogenous opioids. This idea holds that as a consequence of intense aerobic exercise, opioids are released in the body and create a feeling of euphoria, relaxation and calm. But for several years, research has been accumulating suggesting that endocannabinoids, and the endocannabinoid system, provide the basis for the runner’s high. This study set out to further investigate whether opioids or endocannabinoids are responsible for the sense of well-being that accompanies running, using a simple and elegant research design.
Who was it?
Sixty three healthy adults (32 men and 32 women) between the ages of 18 and 50 who regularly perform endurance exercise were recruited to the study. Subjects were asked to refrain from drinking and eating two hours before data collection and to avoid nicotine and caffeine on the day of testing.
What was done?
This was a double-blind, placebo-controlled study. Each subject performed two exercise conditions, walking and running, in a random order. Each subject was assigned to either take naltrexone, a central opioid blocker, or a placebo, prior to each exercise condition. Subjects completed psychological tests to determine their emotional states. Anxiety was further assessed using a specialized test. Blood samples were collected before and after exercise and levels of opioids and endocannabinoids (including anandamide and 2-arachidonylglycerol, 2-AG) were measured.
Both running and walking stimulated a release of endocannabinoids, although the increase was higher for running. Feelings of euphoria were much higher with running than walking, while anxiety was much lower. Treatment with naltrexone, which blocked opioid receptors in the brain, did not dampen the experience of euphoria or blunt the reduction in anxiety, demonstrating that these states were not mediated by opioid levels.
This study provides further evidence that the “runner’s high” is a function of endocannabinoids, rather than opioids, in the brain. Endocannabinoids can be increased in a variety of ways, including taking phytocannabinoids such as CBD and engaging in exercise and pleasurable activities like singing and dancing. Combining strategies that boost endocannabinoid levels could be recommended to patients as part of a general “toolbox” to improve feelings of health and well-being.