'Runner's High' Similar to Marijuana High, Researchers Say

Findings of a recently-published study in the Proceedings of the National Academy of Sciences provide new, albeit disturbing, information about "runner's high."

Led by Dr. Johannes Fuss and colleagues at the University of Heidelberg in Mannheim, Germany explored, as per The Daily Beast, the research explored and analyzed how endocannabinoids, the body's version of cannabis or marijuana, are responsible for the euphoric feeling of a runner's high - challenging the well-known theory of brain receptors, reducing a runner's perception of pain and giving the body a "euphoric boost."

A report by The Washington Post describes endocannabinoids "as the body's self-produced marijuana" and like cannabis, "can impact a wide range of physiological processes, including appetite, pain, memory and mood."

To test their hypothesis, the researchers experimented with mice by equipping them with running wheels. "If you place a running wheel in a mouse's cage, it will run voluntarily, covering great distances of about 10 km/day over twelve hours each day," Fuss says as told by The Daily Beast.

"They're really motivated to run; there are strong biological processes motivating these mice to run in running wheels, therefore they're a good model to study why humans are motivated to do exercise," he explains in the same report.

According to The Washington Post, the mice were less anxious and handled pain better after the runs. After which, Fuss and colleagues then made use of drugs to block the mice's endocannabinoid system, as per The Washington Post. The results were a stark contrast with the former.

"What we found was blocking the endorphin receptors didn't change anything physically. The mice were still running and still less anxious, and they still experienced less pain. In contrast, when blocking endocannabinoid receptors, the mice were no longer less anxious or had reduced pain sensitivity," the researchers write as quoted by The Daily Beast.

In the last experiment, Fuss genetically altered a group of mice, describing their forebrain as having no cannabinoid receptors. Simply put, the mice are incapable of experiencing a runner's high. Fuss and colleagues observed that the mice ran "comparable distances" in the beginning. However, after a couple of days, they slowly ceased to. "Probably because they don't have this emotional benefit from running; it's kind of boring for them," the research team writes.

In the future, Fuss and the team plan to find out which brain structures play a role in the endocannabinoid experiment. "There's also a tremendous amount of research to be done in humans, specifically why some people experience a runner's high and others do not," Fuss notes.