Cannabidiol (CBD) is a phytocannabinoid discovered in 1940. It is one of 113 identified cannabinoids in cannabis plants, along with tetrahydrocannabinol (THC), and accounts for up to 40% of the plant's extract. , clinical research on CBD included studies related to anxiety, cognition, movement disorders, and pain, but there is insufficient high-quality evidence that cannabidiol is effective for these conditions. Nevertheless, CBD is a herbal dietary supplement promoted with unproven claims of particular therapeutic effects. The global market size for CBD was predicted to exceed billion by 2028. Cannabidiol can be taken internally in multiple ways, including by inhaling cannabis smoke or vapor, oral, and as an aerosol spray into the cheek. It may be supplied as CBD oil containing only CBD as the active ingredient (excluding THC or terpenes), CBD-dominant hemp extract oil, capsules, dried cannabis, or prescription liquid solution. CBD does not have the same psychoactivity as THC, and can negate the psychoactive effects of THC on the body if both are present. CBD heated to 250–300 °C may partially be converted into THC. , the mechanism of action for its biological effects had not been determined. Unlike THC, which acts on the cannabinoid receptor type 1 (CB1) as a partial agonist, CBD instead is a negative allosteric modulator of CB1 receptors. In the United States, the cannabidiol drug Epidiolex was approved by the Food and Drug Administration in 2018 for the treatment of two epilepsy disorders. While the 2018 United States Farm Bill removed hemp and hemp extracts (including CBD) from the Controlled Substances Act, the marketing and sale of CBD formulations for medical use or as an ingredient in dietary supplements or manufactured foods remains illegal under FDA regulation, . Medical uses Cannabidiol is the generic name of the drug and its . Research , there was limited high-quality evidence for cannabidiol having a neurological effect in humans. Epilepsy In the United States, the FDA has indicated only one brand of prescription cannabidiol called Epidiolex for the treatment of seizures associated with Dravet syndrome, Lennox–Gastaut syndrome, or tuberous sclerosis complex in people one year of age and older. While Epidiolex treatment is generally well tolerated, it is associated with minor adverse effects, such as gastrointestinal upset, decreased appetite, lethargy, sleepiness and poor sleep quality. In the European Union, cannabidiol (Epidyolex) is indicated for use as adjunctive therapy of seizures associated with Lennox–Gastaut syndrome or Dravet syndrome,