LAUSR

K IM B E R LY B O Y LE S / S H U TT E R S TO C K .C O M O ver the past decade, marijuana has had quite a run. Seventeen US states and the District of Columbia now allow recreational use of marijuana; only 13 states have not yet legalized it for either medical or recreational purposes. But what do we really know about the relative benefits and risks of the popular and remarkably complex cannabis plant? Researchers have long asserted that the science has badly trailed the claims and counterclaims of supporters and detractors. Over the past 5 years, however, high-quality trials and reviews have begun to close the gap. Of the cannabis plant’s roughly 140 unique chemical constituents, or phytocannabinoids, 2 of the best studied are Δ-9tetrahydrocannabinol (THC), the plant’s main psychoactive ingredient, and cannabidiol (CBD). In an April 2021 telebriefing on cannabis and health sponsored by the nonprofit journalism service SciLine, experts noted that CBD is gaining prominence mainly because of its significant differences with THC. “What is unique about CBD is that although it is psychoactive— so we think that it is helpful for some indications for the central nervous system and in the brain, like anxiety, and perhaps pain—it is not intoxicating,” says Ziva Cooper, PhD, director of the University of California, Los Angeles Cannabis Research Initiative. Some scientists believe that other phytocannabinoids and hundreds of separate chemicals called terpenes might likewise have therapeutic effects, although Dr. Cooper cautions that most research on these chemicals has so far been limited to animal studies.