Cannabis, also known as marijuana among other names, is a psychoactive drug from the Cannabis plant intended for medical or recreational use. 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 is often used for its mental and physical effects, such as a “high” or “stoned” feeling, a general change in perception, euphoria (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. Studies have found a strong relation between cannabis use and the risk of psychosis,[26] though the cause-and-effect relationship is debated.


Cannabis is mostly used recreationally or as a medicinal drug, although it may also be used for religious or 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). In 2015, 43% of Americans had used cannabis, which increased to 51% in 2016. About 12% have used it in the past year, and 7.3% have used it in the past month. This makes it the most commonly used illegal drug both in the world and the United States.

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 is taking place in Canada, Belgium, Australia, the Netherlands, Germany, Spain, and 23 U.S. states. Cannabis use started to become popular in the US in the 1970s. Support for legalization has increased in the United States and several U.S. states have legalized recreational or medical use.

Main article: Effects of cannabis

A woman smoking a marijuana “joint”.
Cannabis has psychoactive and physiological effects when consumed. The immediate desired effects from consuming cannabis include relaxation and euphoria (the “high” or “stoned” feeling), a general alteration of conscious perception, increased awareness of sensation, increased libido and distortions in the perception of time and space. At higher doses, effects can include altered body image, auditory and/or visual illusions, pseudohallucinations and ataxia from selective impairment of polysynaptic reflexes. In some cases, cannabis can lead to dissociative states such as depersonalization and derealization.

Some immediate undesired side effects include a decrease in short-term memory, dry mouth, impaired motor skills and reddening of the eyes. Aside from a subjective change in perception and mood, the most common short-term physical and neurological effects include increased heart rate, increased appetite and consumption of food, lowered blood pressure, impairment of short-term and working memory, psychomotor coordination, and concentration. Some users may experience an episode of acute psychosis, which usually abates after six hours, but in rare instances, heavy users may find the symptoms continuing for many days. A reduced quality of life is associated with heavy cannabis use, although the relationship is inconsistent and weaker than for tobacco and other substances

See also: War on Drugs, Legal history of cannabis in the United States, History of medical cannabis, and Timeline of cannabis

The Chinese character for hemp (? or má) depicts two plants under a shelter. Cannabis cultivation dates back at least 3000 years in Taiwan.
Cannabis is indigenous to Central and South Asia. There is evidence of inhalation of cannabis smoke from the 3rd millennium BC, namely charred cannabis seeds found in a ritual brazier at an ancient burial site in present-day Romania. The earliest written reference to cannabis dates back to 2727 BC, from the Chinese emperor Shennong.

In 2003, a leather basket filled with cannabis leaf fragments and seeds was found next to a 2,500- to 2,800-year-old mummified shaman in the northwestern Xinjiang Uygur Autonomous Region of China. Evidence of cannabis consumption was also found in Egyptian mummies dated about 950 BC.

Hemp is called ganja (Sanskrit: ?????, IAST: gañja) in Sanskrit and other modern Indo-Aryan languages. Some scholars suggest that the ancient drug soma, mentioned in the Vedas, was cannabis, although this theory is disputed.

Cannabis was also known to the ancient Assyrians, who discovered its psychoactive properties through the Aryans.[175] Using it in some religious ceremonies, they called it qunubu (meaning “way to produce smoke”), a probable origin of the modern word “cannabis”. The Aryans also introduced cannabis to the Scythians, Thracians and Dacians, whose shamans (the kapnobatai—”those who walk on smoke/clouds”) burned cannabis flowers to induce trance.

Cannabis sativa from Vienna Dioscurides, AD 512
Cannabis has an ancient history of ritual use and is found in pharmacological cults around the world. Hemp seeds discovered by archaeologists at Pazyryk suggest early ceremonial practices like eating by the Scythians occurred during the 5th to 2nd century BC, confirming previous historical reports by Herodotus. It was used by Muslims in various Sufi orders as early as the Mamluk period, for example by the Qalandars. Smoking pipes uncovered in Ethiopia and carbon-dated to around c. AD 1320 were found to have traces of cannabis.

A study published in the South African Journal of Science showed that “pipes dug up from the garden of Shakespeare’s home in Stratford-upon-Avon contain traces of cannabis.” The chemical analysis was carried out after researchers hypothesized that the “noted weed” mentioned in Sonnet 76 and the “journey in my head” from Sonnet 27 could be references to cannabis and the use thereof. Examples of classic literature featuring cannabis include Les paradis artificiels by Charles Baudelaire and The Hasheesh Eater by Fitz Hugh Ludlow.

In the mid-1800s, Irish physician William Brooke O’Shaughnessy, who had studied the drug while working as a medical officer in Bengal with the East India company, brought a quantity of cannabis with him on his return to Britain in 1842, provoking renewed interest in the West.

John Gregory Bourke described the use of “mariguan”, which he identifies as Cannabis indica or Indian hemp, by Mexican residents of the Rio Grande region of Texas in 1894. He described its uses for treatment of asthma, to expedite delivery, to keep away witches, and as a love-philtre. He also wrote that many Mexicans added the herb to their cigarritos or mescal, often taking a bite of sugar afterward to intensify the effect. Bourke wrote that because it was often used in a mixture with toloachi (which he inaccurately describes as Datura stramonium), mariguan was one of the several plants known as “loco weed”. Bourke compared mariguan to hasheesh, which he called “one of the greatest curses of the East”, citing reports that users “become maniacs and are apt to commit all sorts of acts of violence and murder”, causing degeneration of the body and an idiotic appearance, and mentioned laws against sale of hasheesh “in most Eastern countries”.

Cannabis indica fluid extract, American Druggists Syndicate, pre-1937
Cannabis was criminalized in various countries beginning in the early 20th century. In the United States, the first restrictions on sale of cannabis came in 1906 (in District of Columbia).It was outlawed in Jamaica (then a British colony) in 1913, in South Africa in 1922, and in the United Kingdom and New Zealand in the 1920s.[188] Canada criminalized cannabis in The Opium and Narcotic Drug Act, 1923, before any reports of the use of the drug in Canada. In 1925 a compromise was made at an international conference in The Hague about the International Opium Convention that banned exportation of “Indian hemp” to countries that had prohibited its use, and requiring importing countries to issue certificates approving the importation and stating that the shipment was required “exclusively for medical or scientific purposes”. It also required parties to “exercise an effective control of such a nature as to prevent the illicit international traffic in Indian hemp and especially in the resin”.

In the United States in 1937, the Marihuana Tax Act was passed, and prohibited the production of hemp in addition to cannabis. The reasons that hemp was also included in this law are disputed—several scholars have claimed that the act was passed in order to destroy the US hemp industry, with the primary involvement of businessmen Andrew Mellon, Randolph Hearst, and the Du Pont family. But the improvements of the decorticators, machines that separate the fibers from the hemp stem, could not make hemp fiber a very cheap substitute for fibers from other sources because it could not change that basic fact that strong fibers are only found in the bast, the outer part of the stem. Only about 1/3 of the stem are long and strong fibers. The company DuPont and many industrial historians dispute a link between nylon and hemp. They argue that the purpose of developing the nylon was to produce a fiber that could be used in thin stockings for females and compete with silk.

The United Nations’ 2012 Global Drug Report stated that cannabis “was the world’s most widely produced, trafficked, and consumed drug in the world in 2010”, identifying that between 119 million and 224 million users existed in the world’s adult (18 or older) population.

Gateway drug
Main article: Gateway drug theory
The Gateway Hypothesis states that cannabis use increases the probability of trying “harder” drugs. The hypothesis has been hotly debated as it is regarded by some as the primary rationale for the United States prohibition on cannabis use. A Pew Research Center poll found that political opposition to marijuana use was significantly associated with concerns about health effects and whether legalization would increase marijuana use by children.

Some studies state that while there is no proof for the gateway hypothesis, young cannabis users should still be considered as a risk group for intervention programs. Other findings indicate that hard drug users are likely to be poly-drug users, and that interventions must address the use of multiple drugs instead of a single hard drug. Almost two-thirds of the poly drug users in the “2009/10 Scottish Crime and Justice Survey” used cannabis.

The gateway effect may appear due to social factors involved in using any illegal drug. Because of the illegal status of cannabis, its consumers are likely to find themselves in situations allowing them to acquaint with individuals using or selling other illegal drugs. Utilizing this argument some studies have shown that alcohol and tobacco may additionally be regarded as gateway drugs; however, a more parsimonious explanation could be that cannabis is simply more readily available (and at an earlier age) than illegal hard drugs. In turn alcohol and tobacco are easier to obtain at an earlier point than is cannabis (though the reverse may be true in some areas), thus leading to the “gateway sequence” in those individuals since they are most likely to experiment with any drug offered.

An alternative to the gateway hypothesis is the common liability to addiction (CLA) theory. It states that some individuals are, for various reasons, willing to try multiple recreational substances. The “gateway” drugs are merely those that are (usually) available at an earlier age than the harder drugs. Researchers have noted in an extensive review, Vanyukov et al., that it is dangerous to present the sequence of events described in gateway “theory” in causative terms as this hinders both research and intervention