Cannabidiol (CBD) is a phytocannabinoid discovered in 1940. It is one of some 113 identified cannabinoids in cannabis plants and accounts for up to 40% of the plant's extract. 2018 preliminary clinical research on cannabidiol included studies of anxiety, cognition, movement disorders, and pain.
Cannabidiol can be taken into the body in multiple ways, including by mouth via tinctures, supplements or edibles, inhalation of hemp smoke or vapor, as an aerosol spray into the cheek. It may be supplied as CBD oil (containing only CBD as the active ingredient. No added tetrahydrocannabinol [THC] or terpenes), a full-plant CBD-dominant hemp extract oil, capsules, dried hemp, or as a prescription liquid solution. CBD does not have the same psychoactivity as THC and may affect the actions of THC. Although in vitro studies indicate CBD may interact with different biological targets, including cannabinoid receptors and other neurotransmitter receptors, as of 2018 the mechanism of action for its biological effects has not been determined.
In the United States, the cannabidiol drug Epidiolex has been approved by the Food and Drug Administration for treatment of two epilepsy disorders. The side effects of long-term use of the drug include somnolence, decreased appetite, diarrhea, fatigue, malaise, weakness, and sleeping problems.
The U.S. Drug Enforcement Administration has assigned Epidiolex a Schedule V classification, while non-Epidiolex CBD remains a Schedule I drug prohibited for any use. Cannabidiol is not scheduled under any United Nations drug control treaties, and in 2018 the World Health Organization recommended that it remain unscheduled.
As of 2018, due to the passed Agricultural Improvement Act of 2018, hemp-derived CBD (no added tetrahydrocannabinol [THC] or terpenes) is federally legal in all 50 states in the U.S.A.