Cannabis (Cannabis sativa) is a plant with many uses. As a drug, it is the most popular recreational drug around the world, and the fourth most-used psychoactive substance after tobacco, alcohol, and caffeine. It can be consumed in the form of dried infructescences, resins, and various extracts collectively known as hashish or weed. Cannabis is a flowering plant with long, broad leaves that may be palmately compound or digitate, with serrate leaflets. It is wind-pollinated, and the fruit is an achene. Cannabis is dioecious, but it is often cultivated as monoecious for drug use and textile fiber production.
The plant has several cannabinoid chemicals, including THC and CBD, which have psychoactive effects when smoked or vaporized. These chemicals can change the way a person experiences and thinks about things, and affect aspects of behavior like memory, thinking, concentration, movement, coordination, and sensory and time perception. Cannabis can also cause feelings of relaxation, anxiety, and euphoria.
In some cases, scientists have used the chemical compounds in marijuana to treat certain medical conditions. For example, a medicine called dronabinol (brand name Marinol) is approved by the Food and Drug Administration to treat seizures associated with two rare forms of epilepsy. Other medicines derived from the cannabis plant—including THC—are approved to treat nausea and vomiting associated with cancer chemotherapy, and to increase appetite in people living with HIV/AIDS. They are also being tested in clinical trials for PTSD and other conditions. Despite its potential medicinal value, researchers remain concerned about the potential side effects of cannabis.