Cannabis is a genus of flowering plants in the family Cannabaceae. The number of species within the genus is disputed. Three species may be recognized: Cannabis sativa, Cannabis indica, and Cannabis ruderalis. The genus is widely accepted as being indigenous to and originating from Central Asia, with some researchers also including upper South Asia in its origin.
The plant is also known as hemp, although this term is often used to refer only to varieties of Cannabis cultivated for non-drug use. Cannabis has long been used for hemp fiber, hemp seeds, and their oils, hemp leaves for use as vegetables and as juice, medicinal purposes, and as a recreational drug. Industrial hemp products are made from cannabis plants selected to produce an abundance of fiber. To satisfy the UN Narcotics Convention, some cannabis strains have been bred to produce minimal levels of tetrahydrocannabinol (THC), the principal psychoactive constituent. Some strains have been selectively bred to produce a maximum of THC (a cannabinoid), the strength of which is enhanced by curing the flowers. Various compounds, including hashish and hash oil, are extracted from the plant.
Globally, in 2013, 60,400 kilograms of cannabis were produced legally. In 2014 there were an estimated 182.5 million cannabis users (3.8% of the population aged 15–64). This percentage has not changed significantly between 1998 and 2014.
Cannabis is an annual, dioecious, flowering herb. The leaves are palmately compound or digitate, with serrate leaflets. The first pair of leaves usually have a single leaflet, the number gradually increasing up to a maximum of about thirteen leaflets per leaf (usually seven or nine), depending on variety and growing conditions. At the top of a flowering plant, this number again diminishes to a single leaflet per leaf. The lower leaf pairs usually occur in an opposite leaf arrangement and the upper leaf pairs in an alternate arrangement on the main stem of a mature plant.
The leaves have a peculiar and diagnostic venation pattern that enables persons poorly familiar with the plant to distinguish a cannabis leaf from unrelated species that have confusingly similar leaves. As is common in serrated leaves, each serration has a central vein extending to its tip. However, the serration vein originates from lower down the central vein of the leaflet, typically opposite to the position of, not the first notch down, but the next notch.
The use of Cannabis as a mind-altering drug has been documented by archaeological finds in prehistoric societies in Eurasia and Africa. The oldest written record of cannabis usage is the Greek historian Herodotus' reference to the central Eurasian Scythians taking cannabis steam baths. His (c. 440 BCE) Histories records, "The Scythians, as I said, take some of this hemp-seed [presumably, flowers], and, creeping under the felt coverings, throw it upon the red-hot stones; immediately it smokes, and gives out such a vapor as no Grecian vapor-bath can exceed; the Scyths, delighted, shout for joy." Classical Greeks and Romans were using cannabis, while in the Middle East, use spread throughout the Islamic empire to North Africa. In 1545, cannabis spread to the western hemisphere where Spaniards imported it to Chile for its use as fiber. In North America, cannabis, in the form of hemp, was grown for use in rope, clothing, and paper.
Medical cannabis (or medical marijuana) refers to the use of cannabis and its constituent cannabinoids, to treat disease or improve symptoms. Cannabis is used to reduce nausea and vomiting during chemotherapy, to improve appetite in people with HIV/AIDS, and to treat chronic pain and muscle spasms. Cannabinoids are under preliminary research for their potential to affect stroke.
Short-term use increases both minor and major adverse effects. Common side effects include dizziness, feeling tired, vomiting, and hallucinations. The long-term effects of cannabis are not clear. Concerns including memory and cognition problems, risk of addiction, schizophrenia in young people, and the risk of children taking it by accident.
Cannabis is a popular recreational drug around the world, only behind alcohol, caffeine and tobacco. In the United States alone, it is believed that over 100 million Americans have tried cannabis, with 25 million Americans having used it within the past year.
The psychoactive effects of cannabis are known to have a triphasic nature. Primary psychoactive effects include a state of relaxation, and to a lesser degree, euphoria from its main psychoactive compound, tetrahydrocannabinol. Secondary psychoactive effects, such as a facility for philosophical thinking, introspection, and metacognition have been reported among cases of anxiety and paranoia. Finally, the tertiary psychoactive effects of the drug cannabis can include an increase in heart rate and hunger, believed to be caused by 11-OH-THC, a psychoactive metabolite of THC produced in the liver.
Normal cognition is restored after approximately three hours for larger doses via a pipe, bong or vaporizer. However, if a large amount is taken orally the effects may last much longer. After 24 hours to a few days, minuscule psychoactive effects may be felt, depending on dosage, frequency and tolerance to the drug.
Cannabidiol (CBD), which has no psychotropic effects by itself (although sometimes showing a small stimulant effect, similar to caffeine), attenuates or reduces the higher anxiety levels caused by THC alone.
According to Delphic analysis by British researchers in 2007, cannabis has a lower risk factor for dependence compared to both nicotine and alcohol. However, everyday use of cannabis may be correlated with psychological withdrawal symptoms, such as irritability or insomnia, and susceptibility to a panic attack may increase as levels of THC metabolites rise. However, cannabis withdrawal symptoms are typically mild and are never life-threatening.
The risk of adverse outcomes from cannabis use may be reduced by the implementation of evidence-based education and intervention tools communicated to the public with practical regulation measures.
The legal status of cannabis is changing rapidly. This list may be out of date.
The legality of cannabis for medical and recreational use varies by country, in terms of its possession, distribution, and cultivation, and (in regards to medical) how it can be consumed and what medical conditions it can be used for. These policies in most countries are regulated by the United Nations Single Convention On Drugs that was ratified in 1961, along with the 1971 Convention on Psychotropic Substances and the 1988 Convention against Illicit Traffic in Narcotic Drugs and Psychotropic Substances.
The use of cannabis for recreational purposes is prohibited in most countries; however, many have adopted a policy of decriminalization to make simple possession a non-criminal offense (often similar to a minor traffic violation). Others have much more severe penalties such as in some Asian and Middle Eastern countries where possession of even small amounts is punished by imprisonment for several years.
Uruguay and Canada are the only countries that have fully legalized the consumption and sale of recreational cannabis nationwide. In the United States, ten states and the District of Columbia have legalized sales and consumption although it remains federally illegal. Court rulings in Georgia and South Africa have led to the legalization of the consumption of cannabis, but not legal sales. A policy of limited enforcement has also been adopted in many countries, in particular Spain and the Netherlands where the sale of cannabis is tolerated at licensed establishments.
Countries that have legalized the medical use of cannabis include Australia, Canada, Chile, Colombia, Finland, Germany, Greece, Israel, Italy, Norway, the Netherlands, Peru, Poland, and Thailand. In the United States, 33 states and the District of Columbia have legalized the medical use of cannabis, but at the federal level its use remains prohibited for any purpose.