What is THC?
Tetrahydrocannabinol (THC) is one of the major active cannabinoids found in cannabis. It is the main compound responsible for the psychoactive effects of cannabis, including changes in mental processes (e.g., thoughts, mood, and perception) that cause the feeling of being “high”.[3] While THC is found naturally in cannabis in combination with many other active compounds, like cannabidiol (CBD), some supplements and prescription medications contain isolated THC or synthetic THC analogs, which will be the focus of this page.
What are THC’s main benefits?
THC may have some therapeutic benefits on pain and chemotherapy-induced nausea and vomiting. Despite these potential benefits, THC can induce intoxication and cause other side effects that may reduce the quality of life for some people.[4][5] On the flip side, some people seek out THC recreationally for its intoxicating effects, which can include euphoria, a sense of relaxation, and altered sensory perception.
THC is likely effective for reducing nausea and vomiting in children and adults undergoing chemotherapy. The effects are superior to a placebo and potentially comparable to standard treatments, although more research is needed to confirm the latter.[6][7] While THC might reduce nausea and vomiting in other contexts, this hasn’t been thoroughly researched.
THC may also reduce chronic pain to a small or moderate degree, with most research looking at neuropathic pain of various origins.[8][9] Limited research suggests that THC may also reduce pain due to cancer or multiple sclerosis.[10] Still, how THC compares to commonly used pain relievers is not particularly clear, and when used alongside opioid analgesics, THC doesn’t seem to reduce the required dose of opioids.[11][12]
What are THC’s main drawbacks?
THC is associated with a relatively high risk of side effects that tend to be dose-dependent (occurring more often with increasing doses).
The most common side effects of THC include sedation, dizziness, confusion, impaired cognition, impaired coordination, euphoria, anxiety, paranoia, heightened sensory awareness, headache, dry mouth, increased appetite, and nausea. THC can cause intoxication and impair the ability to drive.[1][13][14]
Less often, THC may cause vomiting, hallucinations, increased heart rate, orthostatic hypotension, and psychosis (in predisposed individuals).[1] There have also been case reports linking THC with an increased risk of seizure or heart attack.[15][16][17]
If THC is inhaled via smoking or vaping, it can increase the risk of lung disease or lung injury. Vaporizing THC can minimize the production of potentially cancer-causing compounds formed through combustion; however, there is still a risk of lung injury with vaping.[3]
How does THC work?
THC exerts its effects by interacting with the body’s endocannabinoid system, which involves binding to and activating the cannabinoid receptors cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2).
The brain and spinal cord are rich in CB1 receptors, which are responsible for most of THC’s effects. When THC activates CB1 receptors, it alters neurotransmission (how neurons communicate) in a way that influences many bodily functions including pain signaling, appetite, cognition, the sleep-wake cycle, and nausea and vomiting. CB2 receptors are found predominantly in immune cells, and their activation by THC may have an anti-inflammatory effect.[9][18]
What are other names for THC
- tetrahydrocannabinol
- Delta-9-tetrahydrocannabinol
- Δ9-Tetrahydrocannabinol
- Nabilone (THC analog)
- Dronabinol (THC analog)
Dosage information
Isolated THC can be taken orally as an extract in oil, capsule, or edible form. Alternatively, THC can be inhaled through smoking or vaporizing dried cannabis or cannabis concentrates. However, the types of THC available will vary depending on the legal status of THC in your region.
The recommended dosage of THC ranges from 2.5 mg to 30 mg daily. In general, it’s recommended to start low, go slow, and stay low to reduce the risk of side effects and minimize tolerance (a reduced response to the drug after repeated use).[1] This might look like starting at a dose of 2.5–5 mg and increasing slowly (every few days or as tolerated) until the desired therapeutic effect is achieved but side effects are kept to a minimum. If using a prescription medication containing a synthetic version of THC, the dosing may not necessarily be equivalent to natural THC.
THC taken orally will have a slower onset (1–3 hours) than inhaled THC, which has a rapid onset (5–10 minutes).[2]
You can estimate the dose of THC in dried cannabis based on the percent of THC in the product. Simply multiply the total dried weight in milligrams (1 gram = 1,000 milligrams) by the percentage of THC in the product. For example, if you have 0.25 g (250 mg) of dried cannabis with 10% THC, it will contain 25 mg of THC (250 mg x 0.10).
Frequently asked questions
Tetrahydrocannabinol (THC) is one of the major active cannabinoids found in cannabis. It is the main compound responsible for the psychoactive effects of cannabis, including changes in mental processes (e.g., thoughts, mood, and perception) that cause the feeling of being “high”.[3] While THC is found naturally in cannabis in combination with many other active compounds, like cannabidiol (CBD), some supplements and prescription medications contain isolated THC or synthetic THC analogs, which will be the focus of this page.
THC may have some therapeutic benefits on pain and chemotherapy-induced nausea and vomiting. Despite these potential benefits, THC can induce intoxication and cause other side effects that may reduce the quality of life for some people.[4][5] On the flip side, some people seek out THC recreationally for its intoxicating effects, which can include euphoria, a sense of relaxation, and altered sensory perception.
THC is likely effective for reducing nausea and vomiting in children and adults undergoing chemotherapy. The effects are superior to a placebo and potentially comparable to standard treatments, although more research is needed to confirm the latter.[6][7] While THC might reduce nausea and vomiting in other contexts, this hasn’t been thoroughly researched.
THC may also reduce chronic pain to a small or moderate degree, with most research looking at neuropathic pain of various origins.[8][9] Limited research suggests that THC may also reduce pain due to cancer or multiple sclerosis.[10] Still, how THC compares to commonly used pain relievers is not particularly clear, and when used alongside opioid analgesics, THC doesn’t seem to reduce the required dose of opioids.[11][12]
THC has been proposed as a potentially useful compound in the management of dementia, particularly for behavioral symptoms like aggression, agitation, trouble sleeping, wandering, and poor dietary intake. Further, some research in rodents has found that activation of cannabinoid receptor 2 (CB2) receptors in immune cells in the brain may reduce neuroinflammation, oxidative stress, and the formation of the amyloid plaques characteristic of Alzheimer’s disease.[32]
A handful of randomized controlled trials, uncontrolled trials, and case reports have suggested that THC and its analogs might improve some of the behavioral and psychological symptoms of dementia, most notably aggression and agitation. THC was usually provided at low dosages (≤5 mg daily) and was reportedly well-tolerated, aside from sedation.[32][33]
However, all studies have been small and short in duration, and the safety of THC (including its effect on cognitive function) has not been adequately explored in this population. Research is fairly consistent in showing that even a single dose of THC can cause short-term impairments in working memory and executive function in an otherwise healthy person, which raises the concern of how it might affect cognition in an older adult with dementia.[34]
Overall, the current evidence of benefit is weak, and, paired with the known negative effects of THC on cognition, using THC in this context seems ill-advised at this time.
THC is well known for its appetite-stimulating effects, more commonly referred to as “the munchies”. While polishing off an entire bag of chips may not be in everyone's best interest, increasing caloric intake may be desired in certain medical conditions where drastic weight loss is contributing to the deterioration of health.
Human immunodeficiency virus (HIV), cancer, and anorexia nervosa can all lead to potentially deleterious weight loss. Preliminary research seems to suggest that THC can stimulate appetite in these populations, leading to increased food intake and potential weight gain; however, the evidence is relatively weak, and it’s not clear whether this translates to improvements in health outcomes or quality of life.[8][14][5]
If you’re interested in learning more, check out our article The Science Behind Munchies: Cannabis And Your Appetite
Our endocannabinoid system is involved in the regulation of emotional and stress responses as well as the consolidation and extinction (forgetting) of memories. Further, some evidence suggests that post-traumatic stress disorder (PTSD) may alter the function of the endocannabinoid system.[35] This has led to the question of whether THC may have a role in the management of PTSD.
Preliminary research has been somewhat promising, although studies have tended to be small, and only a few have been randomized controlled trials. THC may reduce some of the symptoms of PTSD, including a reduction in nightmares, improved sleep, and an increased sense of well-being.[35] Studies looking at brain function have also suggested that THC may reduce the reactivity of the amygdala (the part of the brain involved in detecting danger) in response to a threat, which may help facilitate emotional regulation and fear reduction.[36]
It’s important to consider that people with PTSD have an increased risk of substance use disorder (including cannabis use disorder) and may have other psychiatric conditions that could be worsened through THC exposure.[37] Additionally, an observational study suggested that over time, THC may worsen trauma-related intrusive thoughts.[38]
Clearly, more research is needed to better understand the potential benefits (and risks) of THC in PTSD.
THC, and cannabis in general, are often reported (anecdotally) to improve sleep. In a survey of Canadians who used cannabis for therapeutic purposes, 85% of people reported using cannabis for sleep, making it the most frequently reported use.[39] Despite this, the research is limited, and the results have been fairly mixed.
THC may improve self-reported sleep quality, including reducing the time to fall asleep (sleep latency) and increasing total sleep time. These effects have been the most notable in people with chronic pain but appear less consistently in other populations.[40][11] However, there seems to be a mismatch between subjective and objective measurements of sleep quality. In studies that have monitored brainwave activity, THC has been found to suppress rapid eye movement (REM) sleep and possibly slow-wave sleep (which is important for memory consolidation) with chronic use, and some studies have found increases in sleep latency rather than the self-reported decreases.[40][41][42]
THC is associated with a relatively high risk of side effects that tend to be dose-dependent (occurring more often with increasing doses).
The most common side effects of THC include sedation, dizziness, confusion, impaired cognition, impaired coordination, euphoria, anxiety, paranoia, heightened sensory awareness, headache, dry mouth, increased appetite, and nausea. THC can cause intoxication and impair the ability to drive.[1][13][14]
Less often, THC may cause vomiting, hallucinations, increased heart rate, orthostatic hypotension, and psychosis (in predisposed individuals).[1] There have also been case reports linking THC with an increased risk of seizure or heart attack.[15][16][17]
If THC is inhaled via smoking or vaping, it can increase the risk of lung disease or lung injury. Vaporizing THC can minimize the production of potentially cancer-causing compounds formed through combustion; however, there is still a risk of lung injury with vaping.[3]
Data collected in the United States from 2016 to 2017 found that around 7% of pregnant women reported using cannabis during pregnancy.[19] While potentially helpful for nausea and vomiting, THC is not recommended during pregnancy for several reasons.
The cannabinoid receptor 1 (CB1) receptors that THC exerts its actions through are found in the fetus as early as the first trimester and play an important role in the development of the nervous system. This, paired with the knowledge that THC crosses the placenta, raises a legitimate concern about the effects early exposure to THC might have on the developing fetus.[20]
Observational research suggests that exposure to cannabis during pregnancy may be associated with an increased risk of low birth weight, preterm birth (<37 weeks gestation), small for gestational age diagnosis, and admission to the neonatal intensive care unit (NICU).[21][20] Whether cannabis exposure during pregnancy affects cognitive processes into childhood is poorly researched. However, some preliminary research suggests it may be associated with impairments in attention and a higher likelihood of aggressive and hyperactive behaviors.[20]
Regarding lactation, THC has been found to concentrate in breast milk, meaning levels of THC in breast milk can accumulate and exceed plasma levels in people who use cannabis regularly.[22] Regular use of THC may also affect the composition of breast milk.[23] Still, how THC exposure through breast milk affects an infant in both the short-term and the long-term is poorly researched.[24]
Observational studies have consistently shown that recreational cannabis use is associated with an increased risk of psychosis — a condition that can cause delusions and hallucinations, making it challenging to determine what is reality. While observational studies can’t determine whether cannabis causes psychosis (as opposed to psychosis leading people to use cannabis), the current evidence seems to suggest it. If so, THC is the likely culprit.
Multiple longitudinal cohort studies around the world have generated similar results, finding a dose-dependent relationship between cannabis use and the development of psychosis, even when controlling for multiple confounders.[25][26][27][28][29] Additionally, the relationship does not seem to be influenced by whether someone has a history of psychotic symptoms.[30]
The risk of psychosis seems to be influenced by a number of factors, including the use of higher-potency cannabis (containing higher doses of THC), exposure early in life (i.e., adolescence), long-term cannabis use, and a family or personal history of psychosis.[17][25] Interestingly, a gene variant that influences how dopamine is metabolized in the brain has been linked to an increased risk of psychosis in adolescents exposed to cannabis.[31]
THC exerts its effects by interacting with the body’s endocannabinoid system, which involves binding to and activating the cannabinoid receptors cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2).
The brain and spinal cord are rich in CB1 receptors, which are responsible for most of THC’s effects. When THC activates CB1 receptors, it alters neurotransmission (how neurons communicate) in a way that influences many bodily functions including pain signaling, appetite, cognition, the sleep-wake cycle, and nausea and vomiting. CB2 receptors are found predominantly in immune cells, and their activation by THC may have an anti-inflammatory effect.[9][18]
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