cannabis /kan″əbis/ [Gk, kannabis, hemp] , a psychoactive herb (marijuana) derived from the flowering tops of hemp plants. Prescription use of cannabis for medical purposes is now legal in many states and Canadian provinces. However, the use and possession of marijuana continues to be considered a federal offense. All parts of the plant contain psychoactive substances. Cannabinoids, or psychoactive substances synthesized by the hemp plant, include cannabinol, cannabidiol, cannabinolic acid, cannabigerol, cannabicyclol, and several isomers of tetrahydrocannabinol (THC). THC is believed to cause the most characteristic psychological effects, which include alterations of mood, memory, motor coordination, cognitive ability, and self-perception. Low doses of cannabis commonly hinder complex actions, such as driving and flying, which involve complex sensory perception, concentration, and information processing. Cannabis may also enhance the nondominant senses of touch, taste, and smell. Higher doses in some persons can produce delusions, paranoid feelings, anxiety, and panic. This drug also increases the heart rate and systolic blood pressure. Cannabis is about three times more powerful when smoked than when taken orally. Research indicates that some cannabinoids may be therapeutic as anticonvulsants or antiemetics and may be helpful in reducing intraocular pressure associated with glaucoma. Also called bhang, ganja, grass, hashish, marijuana, pot, reefer, tea, weed. See also medical marijuana.
