Cannabis, also known as marijuana among other names, is a psychoactive drug from the Cannabis plant used for medical or recreational purposes. The main psychoactive part of cannabis is tetrahydrocannabinol (THC), one of 483 known compounds in the plant, including at least 65 other cannabinoids. Cannabis can be used by smoking, vaporizing, within food, or as an extract.
Cannabis has mental and physical effects, such as creating a "high" or "stoned" feeling, a general change in perception, heightened mood, and an increase in appetite. Onset of effects is within minutes when smoked, and about 30 to 60 minutes when cooked and eaten. They last for between two and six hours. Short-term side effects may include a decrease in short-term memory, dry mouth, impaired motor skills, red eyes, and feelings of paranoia or anxiety. Long-term side effects may include addiction, decreased mental ability in those who started as teenagers, and behavioral problems in children whose mothers used cannabis during pregnancy. There is a strong relation between cannabis use and the risk of psychosis, though the cause-and-effect is debated.
Cannabis is mostly used for recreation or as a medicinal drug, although it may also be used for spiritual purposes. In 2013, between 128 and 232 million people used cannabis (2.7% to 4.9% of the global population between the ages of 15 and 65). It is the most commonly used illegal drug both in the world and the United States. The countries with the highest use among adults as of 2018 are Zambia, the United States, Canada, and Nigeria. In 2016, 51% of people in the United States had ever used cannabis. About 12% had used it in the past year, and 7.3% had used it in the past month.
The earliest recorded uses date from the 3rd millennium BC. Since the early 20th century, cannabis has been subject to legal restrictions. The possession, use, and sale of cannabis is illegal in most countries of the world. Medical cannabis refers to the physician-recommended use of cannabis, which takes place in Canada, Belgium, Australia, the Netherlands, Germany, Spain, and 33 U.S. states. In September 2018, cannabis was legalized in South Africa while Canada legalized recreational use of cannabis in October 2018.