What Causes Runner's High?

Some runners are known to get high. No, not from smoking drugs or doing anything illegal, but from running. For a long time, people have associated runner's high with endorphans, but some are critical of that point of view:

What's wrong with the endorphin theory? "Everything," Dietrich said. "The endorphin theory has only survived as a popular myth. In pharmacology, it's been dead a long time. Endorphins are peptides. The beta endorphin is a 31-amino acid chain, a molecule too large to get through the blood-brain barrier."

While endorphans are produced from strenuous exercise, and they are known to reduce our sensitivity to pain, they are not what causes the high feeling some runners get. The high feeling may be directly related to higher anandamide levels. Anadamide levels increase during strenuous exercise, and - unlike endorphins - can cross the blood-brain barrier. Anadamine may also influence brain dopamine levels.

The article also compares runners high with illegal drug usage:

"Releasing dopamine in a natural way, like listening to music or running, does not do the damage a drug does by short circuiting that path," Allan said. "You don't develop a tolerance because the brain doesn't adapt. You have natural mechanisms to handle it. The brain knows how to measure it and how to get rid of it. Whereas with an amphetamine or THC, the brain can't regulate it. You've essentially hit yourself with a sledgehammer. Consequently, your brain doesn't know how to get rid of it. So it soaks up the receptors, thereby creating a tolerance."