Marijuana and fertility Sara Ilnitsky MD, Stan Van Uum MD Canadian Medical Association Journal, 2019 June 10, 191, 23, E638. doi : 10.1503/cmaj.181577 CMAJ Podcasts: author interview at https://soundcloud.com/cmajpodcasts/181577-five   1 Tetrahydrocannabinol acts on the endocannabinoid system, which is ubiquitous in reproductive tissues Tetrahydrocannabinol, the active ingredient in marijuana, is a lipophilic compound with a prolonged half-life of 20–36 hours.1 Tetrahydrocannabinol activates the cannabinoid receptors, which are part of the endogenous endocannabinoid system. This system is found in the hypothalamus, pituitary and internal reproductive organs in both sexes.2,3 2 Marijuana use can decrease sperm count Smoking marijuana more than once weekly in the preceding 3 months (n = 130/1215) [...]