Last Updated: April 11, 2024

Delta-9-tetrahydrocannabinol (THC) is the main psychoactive compound found in cannabis, and it is used both recreationally and medicinally. Evidence suggests that THC may reduce nausea and vomiting due to chemotherapy and neuropathic pain. However, THC comes with a laundry list of downsides that must be considered.

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THC is most often used for

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”. 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 related to 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.[3] 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 or adults undergoing chemotherapy. The effects are superior to placebo and potentially comparable to standard treatments, although more research is needed to confirm the latter. 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.[4] Limited research suggests that THC may also reduce pain due to cancer or multiple sclerosis. 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.[5]

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][6][7]

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.[8]

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.

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.[4][9]

What else is THC known as?
Note that THC is also known as:
  • 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).

Don't miss out on the latest research

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  2. ^Chayasirisobhon SMechanisms of Action and Pharmacokinetics of Cannabis.Perm J.(2020-Dec)
  3. ^Vera Belgers, Jantine G Röttgering, Linda Douw, Martin Klein, Johannes C F Ket, Peter M van de Ven, Thomas Würdinger, Myra E van Linde, Johanna M Niers, Markus Weber, Marcel G Olde Rikkert, Jose Lopez-Sendon, Oscar Arrieta, Kristina B Svendsen, Marcos H N Chagas, Carlos M O de Almeida, Mathilde C M Kouwenhoven, Philip C de Witt HamerCannabinoids to Improve Health-Related Quality of Life in Patients with Neurological or Oncological Disease: A Meta-AnalysisCannabis Cannabinoid Res.(2022 Jul 21)
  4. ^Bradley Sainsbury, Jared Bloxham, Masoumeh Hassan Pour, Mariela Padilla, Reyes EncisoEfficacy of cannabis-based medications compared to placebo for the treatment of chronic neuropathic pain: a systematic review with meta-analysisJ Dent Anesth Pain Med.(2021 Dec)
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