What Really Causes the Runner’s High During Long Runs

The familiar “runner’s high” is real, but experts say it is not mainly caused by endorphins alone. In an interview with The Guardian, brain researchers and sports psychologists said the feeling comes from a mix of neurochemical changes, with the endocannabinoid system now seen as the leading factor.

Dr. Daya Grant, a brain researcher and mental performance consultant, described it as “an orchestra of neurochemical changes” across several brain systems. The body’s endocannabinoids work on pathways affected by cannabis compounds, but they are produced naturally and help regulate pain, reduce stress responses, improve mood, and limit overactivity in nerve cells. Grant said endocannabinoid levels rise during moderate to hard running and remain elevated for about 30 to 45 minutes after a run. A PNAS animal study suggested endorphins cannot easily cross the blood-brain barrier, while endocannabinoids can, which may explain the euphoria and reduced anxiety.

Other chemicals also play a role. Dopamine, linked to motivation and reward, rises during long runs and typically peaks after about 60 minutes. Norepinephrine increases as runners approach their limits, especially in harder workouts, helping maintain alertness and focus.

Experts said not everyone feels the effect because of individual brain chemistry and workout style. Grant said steady aerobic effort at a moderate to hard intensity is most likely to trigger it, while interval training may not produce the same calm euphoria. Dr. Trish Jackman of the University of Lincoln said runner’s high is different from “flow,” which is a state of being fully absorbed when the body and mind feel synchronized, though the two can overlap.

Grant suggested there may also be an evolutionary reason, saying the brain may reward useful effort that once helped humans find food, shelter, and safety. To increase the chances of feeling the high, she and Jackman recommended moderate-hard runs, outdoor settings, varied terrain, and playful route changes, such as trail running or sand, which can also promote flow. Even if the feeling never appears, regular aerobic exercise still delivers major health benefits.