Interest in medical cannabis in the United States has increased rapidly in the past 5 years, and now it is legal in 29 states and the District of Columbia. The evidence base to support the use of medical cannabis has developed too, albeit more slowly. For instance, there have been numerous randomized clinical trials that have evaluated the effectiveness of smoked or vaporized cannabis, as well as targeted trials of its principal cannabinoids, tetrahydrocannabinol (THC), and cannabidiol (CBD).1 Some of the strongest evidence is for neuropathic pain, spasticity associated with multiple sclerosis, and anorexia in the setting of serious illness. On the other hand, other common conditions for which cannabis is often used, such as posttraumatic stress disorder, so far have very little evidence of benefit.