Modern science takes at face value the fact that exercise is beneficial for man’s health. In recent years, medical health professionals have begun to harness exercise as a treatment for a broader range of maladies. Since various studies found increased exercise to correlate with higher levels of endorphins, most believed that the endorphins were directly responsible for what the vernacular dubbed “Runner’s High.” Scientists have sought to either augment or wholly disprove the endorphin hypothesis with further studies. Major Depressive Disorder, or MDD, is an affective condition affecting a significant portion of the general population. Aerobic exercise is increasingly being revealed to be an encouraging treatment for all types of depression and anxiety. The HPA Axis allows one to comfortably exercise without experiencing the extremely stressful symptoms that characterize psychological stress, such as depression, anxiety, fear, etc. Runners’ High is the “…happiness, elation…inner harmony, boundless energy, and…reduction in pain sensation” that ensues following prolonged aerobic activity. Endorphins are the body’s naturally occurring opiates. The Neurogenesis Hypothesis states that “a decrease in the synthesis of new neurons in the adult hippocampus might be linked to major depressive disorder.” Further research implicates BDNF (Brain-Derived Neurotrophin Factor) in exercise-induced neurogenesis. The thought was that beta endorphins are what stimulate increased neurogenesis, in turn causing a decrease in MDD. β-endorphins are large molecules that are too bulky to pass through the BBB and therefore cannot be the cause any changes to occur within the brain. Researchers and scientists have thus turned their attention to endogenous endocannabinoids as the true source of analgesia, sedation, anxiolysis and reduced depression found in endurance exercisers. Chief ligand anandamide (AEA) engenders elevated levels of BDNF (Brain Derived Neurotrophic Factor) during exercise and return-to-baseline levels post-exercise. Endocannabinoids modulate nociception by affecting the Periaqueductal Gray system (PAG). Endogenous cannabinoids and exogenous cannabinoids (marijuana) act in similar fashions, leading to the addictive qualities of exercise. Compelling evidence has ascertained that endogenous endocannabinoids are the underlying cause of the many positive effects of aerobic activity.
Winiarz, E. (2019). Endorphins, Endocannabinoids and Runners’ High. The Science Journal of the Lander College of Arts and Sciences, 13(1). Retrieved from https://touroscholar.touro.edu/sjlcas/vol13/iss1/4