Runners have known it for years: Exercise helps curb the craving for addictive drugs. It’s no different for animals: Rats in cages with running wheels show less interest in amphetamine infusions than rats without exercise options. A recentVanderbilt Universitystudy published in the journal PLoS ONEshowed that heavy marijuana smokers (6 joints per day) with no interest in quitting reported less cannabis use after a modest two-week exercise regimen. In fact, the runner’s high and the cannabis high are more similar than anybody might have previously imagined. Compared to endorphins—the usual explanation for the runner’s high–the painkilling effect produced by the brain’s internal cannabis compounds is much more consistent with the demands of exercise. While high doses of marijuana tend to have a sedating effect, low doses induce activity or hyperactivity. Physical activity may promote cell growth in key areas of the brain involved in addiction, helping to calm the neural whirlwind of withdrawal and craving.