evidence: Professors of pathology, microbiology and immunology Prakash Nagarkatti and Mitzi Nagarkatti write for The Conversation on endocannabinoids, compounds found in humans that are similar to those found in marijuana. [...] But few people know that the human body naturally produces chemicals that are very similar to delta-9-tetrahydrocannabinol, or THC, the psychoactive compound in marijuana, which comes from the Cannabis sativa plant. These substances are called endocannabinoids, and they’re found across all vertebrate species. [...] The cannabis plant contains another compound called cannabidiol, or CBD, which has become popular for its medicinal properties. Unlike THC, CBD doesn’t have psychoactive properties because it does not activate CB1 receptors in the brain. Nor does it activate the CB2 receptors, meaning that its action on immune cells is independent of CB2 receptors.