Marijuana is the most commonly used illicit drug in the United States, with ∼3.1 million individuals reporting daily use in the last year and 8.1 million individuals reporting using marijuana most days in the last month in 2013 (1). Marijuana has now been legalized for medical use in 23 states and the District of Columbia. The process of legalization of marijuana for medical use is substantially different from the approval of medications by the US Food and Drug Administration (FDA): Approval occurs by popular vote or the action of a state legislature, and is thus not subject to the higher standard of evidence required by the FDA for both efficacy and safety. As of April 2015, Colorado, Washington, Alaska, Oregon, and the District of Columbia have also legalized marijuana for recreational use, with other states likely to follow. At the federal level, however, marijuana remains illegal as a schedule I controlled substance, a category reserved for substances with a high potential for abuse, lack of established safety, and no accepted medical use.
