There has been a spate of recent articles on exercise and cannabis. Part of the runner’s high is attributable to endocannabinoid release. In Colorado, cannabis users are more physically active, on average. And in a recent review, Chinese scientists at Shenzhen University describe how the endocannabinoid system may mediate the numerous cognitive effects of exercise. It’s complicated, since activating the endocannabinoid system can augment or reduce cognition, depending on the intensity of activation and the individual’s circumstance. Exercise is an acute stressor. But it’s a healthy stress that engages the body’s homeostatic mechanisms, promoting neurogenesis and other positive adaptations. Regular exercise also improves brain function. The scientists describe specific changes in neurotransmitter pathways that exercise — through the endocannabinoid system — appears to alter. Moderate exercise increases anandamide levels, and this is in turn correlated with elevated mood and greater activity in brain regions that store memory. The authors end with a discussion of the experimental subtleties of probing the relationship between exercise and the endocannabinoid system in humans. A simple and useful experiment would be to test whether or not blocking CB1 receptors prevents some of the benefits of exercise.