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 brainвЂ™s reward pathway (4). Similar to how an endorphin is the naturally produced version of morphine in the body, an endocannabinoid is the bodyвЂ™s version of cannabis. Instead, recent studies have investigated a different molecule as being primarily responsible for producing the runnerвЂ™s high вЂ“ endocannabinoids. 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). However, this common theory has since been called into question. 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). The study proposed that the runnerвЂ™s high is a result of the prolonged release of endorphins, which are natural opioids produced by the body.

The most widespread and popular theory regarding the chemical basis of the runnerвЂ™s high originates from a study in the 1980s that investigated endorphins and subsequent mood changes during long-distance running (2). Exercise in general is known to stimulate the release of a cocktail of mood-boosting neurotransmitters, such as endorphins, dopamine, norepinephrine, and serotonin (1). Many long-distance runners are driven by their pursuit of the вЂњrunnerвЂ™s high,вЂќ which is described to be a feeling of euphoria and invincibility reached after covering lengthy distances.

Endorphin high