Long-term adverse effects may include addiction, decreased mental ability in those who started regular use as adolescents,[4] chronic coughing, susceptibility to respiratory infections, and cannabinoid hyperemesis syndrome.

At higher doses, effects can include altered body image, auditory or visual illusions, pseudohallucinations and ataxia from selective impairment of polysynaptic reflexes.

[29] Cannabis has held sacred status in several religions and has served as an entheogen – a chemical substance used in religious, shamanic, or spiritual contexts[30] – in the Indian subcontinent since the Vedic period.

[51][52][53] Cannabis impairs a person's driving ability, and THC was the illicit drug most frequently found in the blood of drivers who have been involved in vehicle crashes.

[54][55][c] Some immediate undesired side effects include a decrease in short-term memory, dry mouth, impaired motor skills, reddening of the eyes,[58] dizziness, feeling tired and vomiting.

[79][80][81] Cannabis use is associated with increased recruitment of task-related areas, such as the dorsolateral prefrontal cortex, which is thought to reflect compensatory activity due to reduced processing efficiency.

[74] From a clinical perspective, two significant school of thought exists for psychiatric conditions associated with cannabis (or cannabinoids) use: transient, non-persistent psychotic reactions, and longer-lasting, persistent disorders that resemble schizophrenia.

[108] Other side effects of cannabis use include cannabinoid hyperemesis syndrome (CHS), a condition which involves recurrent nausea, cramping abdominal pain, and vomiting.

[126][15] A 2022 study found that smoking cannabis using a bong can greatly increase background levels of fine particulate matter, a carcinogen, in an enclosed space such as a living room.

[131] THC appears to alter mood and cognition through its agonist actions on the CB1 receptors, which inhibit a secondary messenger system (adenylate cyclase) in a dose-dependent manner.

[53] THC and its major (inactive) metabolite, THC-COOH, can be measured in blood, urine, hair, oral fluid or sweat using chromatographic techniques as part of a drug use testing program or a forensic investigation of a traffic or other criminal offense.

[140] Commercial cannabinoid immunoassays, often employed as the initial screening method when testing physiological specimens for marijuana presence, have different degrees of cross-reactivity with THC and its metabolites.

[142] Researchers at John Jay College of Criminal Justice reported that dietary zinc supplements can mask the presence of THC and other drugs in urine.

[143] However, a 2013 study conducted by researchers at the University of Utah School of Medicine refute the possibility of self-administered zinc producing false-negative urine drug tests.

Although herbal cannabis and industrial hemp derive from the same species and contain the psychoactive component (THC), they are distinct strains with unique biochemical compositions and uses.

The oldest archeological evidence for the burning of cannabis was found in Romanian kurgans dated 3,500 BC, and scholars suggest that the drug was first used in ritual ceremonies by Proto-Indo-European tribes living in the Pontic-Caspian steppe during the Chalcolithic period, a custom they eventually spread throughout Western Eurasia during the Indo-European migrations.

[206][207] 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.

[211][212][213] Following an 1836–1840 travel in North Africa and the Middle East, French physician Jacques-Joseph Moreau wrote on the psychological effects of cannabis use; he founded the Paris' Club des Hashischins in 1844.

[214] In 1842, 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, provoking renewed interest in the West.

[215] Examples of classic literature of the period featuring cannabis include Les paradis artificiels (1860) by Charles Baudelaire and The Hasheesh Eater (1857) by Fitz Hugh Ludlow.

[224] Cannabis products are only sold openly in certain local "coffeeshops" and possession of up to 5 grams (0.18 oz) for personal use is decriminalized, however: the police may still confiscate it, which often happens in car checks near the border.

[231] According to Vera Rubin, the use of cannabis has been encompassed by two major cultural complexes over time: a continuous, traditional folk stream, and a more circumscribed, contemporary configuration.

[232] The former involves both sacred and secular use, and is usually based on small-scale cultivation: the use of the plant for cordage, clothing, medicine, food, and a "general use as an euphoriant and symbol of fellowship.

"[232][233] The second stream of expansion of cannabis use encompasses "the use of hemp for commercial manufacturers utilizing large-scale cultivation primarily as a fiber for mercantile purposes"; but it is also linked to the search for psychedelic experiences (which can be traced back to the formation of the Parisian Club des Hashischins).

Many jurisdictions have lessened the penalties for possession of small quantities of cannabis so that it is punished by confiscation and sometimes a fine, rather than imprisonment, focusing more on those who traffic the drug on the black market.

[251] On 17 October 2015, Australian health minister Sussan Ley presented a new law that will allow the cultivation of cannabis for scientific research and medical trials on patients.

[254] This legalization comes with regulation similar to that of alcohol in Canada, age restrictions, limiting home production, distribution, consumption areas and sale times.

[257] As the drug has increasingly been seen as a health issue instead of criminal behavior, cannabis has also been legalized or decriminalized in: Czech Republic,[258] Colombia,[259][260] Ecuador,[261][262][263] Portugal,[264] South Africa[265] and Canada.

[298][299] A Pew Research Center poll found that political opposition to marijuana use was significantly associated with concerns about the health effects and whether legalization would increase cannabis use by children.

[citation needed] In turn, alcohol and tobacco are typically easier to obtain at an earlier age 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.