Runner’s high uses same system as marijuana

By Staff Writer • Published: August 22nd, 2017
Category: Health in a Heartbeat

People have long credited endorphins, released during exercise, for the pleasant feeling of the so-called runner’s high.

But scientists know that endorphin molecules can’t cross the blood-brain barrier. It turns out something a little more closely associated with a couch and a bunch of snacks may be responsible for exercise-induced euphoria: endocannabinoids. The endocannabinoid system is the same system that allows the brain to experience the psychoactive effect of marijuana.

In their study, researchers in Germany gave mice access to a running wheel for three days, then blocked that access for the next two days. Then the mice were divided into running and non-running groups. On Day 6, the mice were taken into a room with light controls. The running group had access to a wheel for five hours and the non-running group did not.

The mice were placed in a dark container with access to light. The non-running mice tended to stay in the dark while the running mice explored the lit areas. This was a test of anxiety: Less anxious mice ventured into lit areas.

Then mice were placed on a plate that heated up until mice showed early signs of non-harmful pain. The running group licked their hind paws and jumped less, suggesting a higher tolerance for the heat.

When the scientists blocked the endocannabinoid system but left endorphin receptors open, the running group exhibited the same anxiety as the non-running group.

The only drawback? The running mice ran about three miles per day — which could translate into quite a distance for human runners. Still, exercise offers a healthy way to experience a happy feeling.