Marathon Running Triggers Endocannabinoid Surge, Study Finds

Researchers led by psychiatrist Michael Siebers of the University of Duisburg-Essen conducted two field investigations of experienced endurance athletes. In the first study, 19 runners completed a marathon around Lake Baldeney in Essen, Germany, while the same individuals performed a matched-duration walk on a separate day. Blood was drawn before the race, at two mid-marathon stops, at the finish line, and again after 45 minutes of rest; participants also reported happiness, anxiety, and pain levels.

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The second study involved 36 athletes who ran 100 km, 160 km, or 230 km in the TorTour de Ruhr ultramarathon, with blood samples taken before and after each distance.

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Two endogenous cannabinoids were tracked: anandamide and 2-AG. Anandamide levels rose steadily from 14 km (? 8 miles) onward, staying significantly higher than during the matched walk and remaining elevated 45 minutes post-finish. By contrast, 2-AG increased only near the marathon’s end and persisted through recovery. The researchers note that the messengers follow distinct biochemical pathways, explaining their divergent time courses “Anandamide and 2-AG are produced and degraded through different biochemical pathways, so it is not surprising that they followed different time courses,” — Michael Siebers.

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Relative to walking, marathon running produced greater reported happiness and lower anxiety, while pain rose sharply after 28 km. In the ultramarathon cohort, anxiety declined but happiness did not rise appreciably; only 12 of the 36 participants described experiencing a runner’s high. Siebers emphasized the difficulty of capturing this phenomenon scientifically “The runner's high is a difficult phenomenon to capture scientifically,” — Michael Siebers and warned that elevated endocannabinoid levels alone are insufficient to generate the high “Elevated endocannabinoid levels alone are not sufficient to produce a runner's high,” — Michael Siebers.

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The authors acknowledge several constraints: small sample sizes, reliance on blood rather than brain measurements, and incomplete control of variables such as sleep, nutrition, and stress. Although prior mouse work suggested cannabinoid receptors can reduce anxiety and pain after running, a direct causal link in humans remains unproven. Nonetheless, the findings offer a detailed view of the chemical trajectory accompanying real-world endurance exercise.

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• “Anandamide and 2-AG are produced and degraded through different biochemical pathways, so it is not surprising that they followed different time courses,” — Michael Siebers

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• “The runner's high is a difficult phenomenon to capture scientifically,” — Michael Siebers

ScienceAlert

• “Elevated endocannabinoid levels alone are not sufficient to produce a runner's high,” — Michael Siebers

ScienceAlert