Effects of cannabis
The short-term 'effects of cannabis' are caused by many chemical compounds in the cannabis plant, including 113 different cannabinoids, such as tetrahydrocannabinol, and 120 terpenes, which allow its drug to have various psychological and physiological effects on the human body. Different plants of the genus Cannabis contain different and often unpredictable concentrations of THC and other cannabinoids and hundreds of other molecules that have a pharmacological effect, so the final net effect cannot reliably be foreseen.
Acute effects while under the influence can sometimes include euphoria or anxiety.
Background and chronic use
In the United States, medical cannabis research is limited by federal restrictions.Cannabis use disorder is defined as a medical diagnosis in the fifth revision of the Diagnostic and Statistical Manual of Mental Disorders.
Chemistry
Cannabinoids and cannabinoid receptors
The most prevalent psychoactive substances in cannabis are cannabinoids, particularly THC. Some varieties, having undergone careful selection and growing techniques, can yield as much as 34% THC. Another psychoactive cannabinoid present in Cannabis sativa is tetrahydrocannabivarin, but it is only found in small amounts and is a cannabinoid antagonist.There are similar compounds in cannabis that do not exhibit psychoactive response but are obligatory for functionality: cannabidiol, an isomer of THC; cannabivarin, an analog of cannabinol with a different side chain, cannabidivarin, an analog of CBD with a different side chain, and cannabinolic acid. CBD is believed to regulate the metabolism of THC by inactivating cytochrome P450 enzymes that metabolize drugs; one such mechanism is via generation of carbon monoxide upon metabolism of CBD. THC is converted rapidly to 11-hydroxy-THC, which is also pharmacologically active, so the euphoria outlasts measurable THC levels in blood.
Biochemical mechanisms in the brain
Cannabinoids usually contain a 1,1'-di-methyl-pyran ring, a variedly derivatized aromatic ring and a variedly unsaturated cyclohexyl ring and their immediate chemical precursors, constituting a family of about 60 bi-cyclic and tri-cyclic compounds. Like most other neurological processes, the effects of cannabis on the brain follow the standard protocol of signal transduction, the electrochemical system of sending signals through neurons for a biological response. It is now understood that cannabinoid receptors appear in similar forms in most vertebrates and invertebrates and have a long evolutionary history of 500 million years. The binding of cannabinoids to cannabinoid receptors decrease adenylyl cyclase activity, inhibit calcium N channels, and disinhibit K+A channels. There are at least two types of cannabinoid receptors.Sustainability in the body
Most cannabinoids are lipophilic compounds that are easily stored in fat, thus yielding a long elimination half-life relative to other recreational drugs. The THC molecule, and related compounds, are usually detectable in drug tests from 3 days up to 10 days. Long-term users can produce positive tests for two to three months after ceasing cannabis use.Toxicities
When cannabis is smoked, blood levels of THC peak rapidly after a few minutes and then decline, although the psychotropic effects persist for longer. Edible forms of cannabis often contain tens to hundreds of milligrams of THC, much more than the 32 mg of a typical cannabis cigarette. The rise of edible cannabis products has been responsible for a large increase of poisoning of children and young people. Symptoms in children can include lethargy, sedation and seizure.Synthetic cannabis is suspected of being a potential contributory factor or direct cause of sudden death, due to the strain it can place on the cardiovascular system, or because of cannabinoid hyperemesis syndrome.
Related to cannabinoids
, the principal psychoactive constituent of the cannabis plant, has an extremely low toxicity and the amount that can enter the body through the consumption of cannabis plants poses no threat of death. In dogs, the minimum lethal dose of THC is over 3000 mg/kg. According to The Merck Index, the of THC is 1270 mg/kg for male rats and 730 mg/kg for female rats from oral consumption in sesame oil, and 42 mg/kg for rats from inhalation.Cannabinoids and other molecules present in cannabis can alter the metabolism of other drugs, especially due to competition for clearing metabolic pathways such as cytochromes CYP450, thus leading to drug toxicities by medications that the person consuming cannabis may be taking.
Related to smoking
As of 2025, no high-quality evidence has been found linking cannabis smoking to lung cancer, despite cannabis smoke having similar properties to tobacco smoke. Why this is the case remains unclear. Various studies have speculated that differences in patterns of use compared to tobacco could account for the difference, as well as the anti-inflammatory properties of certain cannabinoids. The health effects of cannabis smoke are an area of active study.A 2007 study found that while tobacco and cannabis smoke are quite similar, cannabis smoke contained higher amounts of ammonia, hydrogen cyanide, and nitrogen oxides, but lower levels of carcinogenic polycyclic aromatic hydrocarbons. This study found that directly inhaled cannabis smoke contained as much as 20 times as much ammonia and 5 times as much hydrogen cyanide as tobacco smoke and compared the properties of both mainstream and sidestream smoke. Mainstream cannabis smoke was found to contain higher concentrations of selected polycyclic aromatic hydrocarbons than sidestream tobacco smoke. However, other studies have found much lower disparities in ammonia and hydrogen cyanide between cannabis and tobacco, and that some other constituents are either lower or non-existent in cannabis smoke. A 2021 longitudinal study conducted among populations of HIV-positive and HIV-negative adults found that smoke-related carcinogenic toxicants and biomarkers detected in tobacco smokers were also detected in exclusive cannabis smokers, including carbon monoxide, polycyclic aromatic hydrocarbons, aldehydes, acrylonitrile and acrylamide metabolites, but exposures are lower compared with tobacco or dual smokers. Increased levels of acrolein exposure by tobacco smoking but not exclusive cannabis smoking were detected both in HIV-positive and HIV-negative adults, and contribute to increased diagnoses of cardiovascular diseases and respiratory diseases among tobacco smokers.
Cannabis smoke contains thousands of organic and inorganic chemical compounds. This tar is chemically similar to that found in tobacco smoke or cigars. Over fifty known carcinogens have been identified in cannabis smoke. These include nitrosamines, reactive aldehydes, and polycylic hydrocarbons, including benzpyrene. Cannabis smoke was listed as a cancer agent in California in 2009. A study by the British Lung Foundation published in 2012 identifies cannabis smoke as a carcinogen and also finds awareness of the danger is low compared with the high awareness of the dangers of smoking tobacco particularly among younger users. Other observations include possible increased risk from each cigarette; lack of research on the effect of cannabis smoke alone; low rate of addiction compared to tobacco; and episodic nature of cannabis use compared to steady frequent smoking of tobacco. Professor David Nutt, a UK drug expert, points out that the study cited by the British Lung Foundation has been accused of both "false reasoning" and "incorrect methodology". Further, he notes that other studies have failed to connect cannabis with lung cancer, and accuses the BLF of "scaremongering over cannabis".
Related to vaping
In 2019 and 2020, severe lung illness from unregulated vapes was strongly linked to vitamin E acetate by the United States Centers for Disease Control and Prevention.A common chemical found in e-cigarettes is ketene. When it enters the lungs after being inhaled, this chemical causes damage to the cellular structure of lung tissue causing the cells to not function at maximum capacity and not absorb gasses as readily. This can cause shortness of breath which can lead to other health conditions such as tachycardia and respiratory failure.
Short-term effects
Onset and duration
When smoked, the short-term effects of cannabis manifest within seconds and are fully apparent within a few minutes, typically lasting 1–3 hours, varying by the person and the strain of cannabis. With oral ingestion, however, the onset of effect is delayed, taking 30 minutes to 2 hours, but the duration is prolonged due to continued slow absorption. The duration of noticeable effects has been observed to diminish after prolonged, repeated use leading to the development of increased tolerance to cannabinoids.Psychological effects
The psychoactive effects of cannabis, known as a "high", or being "stoned", etc., are subjective and vary among persons and the method of use.When THC enters the blood stream and reaches the brain, it binds to cannabinoid receptors. The endogenous ligand of these receptors is anandamide, the effects of which THC emulates. This agonism of the cannabinoid receptors results in changes in the levels of various neurotransmitters, especially dopamine and norepinephrine, which are closely associated with the acute effects of cannabis ingestion, such as euphoria and anxiety.
Some effects may include a general altered state of consciousness, euphoria, relaxation or stress reduction, increased appreciation of the arts, including humor and music, joviality, metacognition and introspection, enhanced recollection, and increased sensuality, sensory awareness, libido, and creativity. Abstract or philosophical thinking, disruption of linear memory and paranoia or anxiety are also typical. Anxiety is cannabis's most commonly reported adverse side effect. Up to 30 percent of recreational users experience intense anxiety and/or panic attacks after smoking cannabis. Some report anxiety only after not smoking cannabis for a prolonged period of time. Inexperience and use in an unfamiliar environment are major contributing factors to this anxiety. Cannabidiol, another cannabinoid found in cannabis, has been shown to mitigate THC's adverse effects, including anxiety.
Cannabis produces many other subjective effects, including increased enjoyment of food taste and aroma, and marked distortions in the perception of time. At higher doses, effects can include altered body image, auditory or visual illusions, pseudohallucinations, and ataxia from selective impairment of polysynaptic reflexes. In some cases, cannabis can lead to acute psychosis and dissociative states such as depersonalization and derealization.
Furthermore, even in those with no family history of psychosis, the administration of pure THC in clinical settings has been demonstrated to elicit transient psychotic symptoms. Any episode of acute psychosis that accompanies cannabis use usually abates after six hours, but in rare instances, users may find the symptoms continuing for many days.
While psychoactive drugs are typically categorized as stimulants, depressants, or hallucinogens, cannabis exhibits a mix of all of these effects. Scientific studies have suggested that other cannabinoids like CBD may also play a significant role in its psychoactive effects.