Tetrahydrocannabinol (THC), in full delta-9-tetrahydrocannabinol, is the main intoxicating compound in cannabis. It acts on CB1 receptors in the brain, which causes the "high", and it can impair memory and attention and trigger anxiety or paranoia in some people. CBD, its close chemical relative, is not intoxicating.
Key facts
- Full name
- Δ9-tetrahydrocannabinol (delta-9-THC); molecular formula C21H30O2, the same as CBD
- Isolated
- 1964, by Yehiel Gaoni and Raphael Mechoulam
- In the plant
- Mostly present as THCA, a non-intoxicating acid that heat converts into THC
- How it acts
- Partial agonist at the CB1 and CB2 cannabinoid receptors
- Dependence risk
- About 9% of people who use cannabis develop dependence at some point (US survey data)
- Legal status (as of October 2026)
- Controlled in most countries; hemp products are allowed only below set THC limits that differ by country
What does tetrahydrocannabinol mean?
The name describes the molecule. "Cannabinol" (CBN) was the first cannabinoid ever isolated from cannabis resin, in the late 19th century (Maioli 2022). "Tetrahydro" means four extra hydrogen atoms: THC has the formula C21H30O2 and CBN C21H26O2 (PubChem). When THC is exposed to air over time, it oxidises and slowly turns into CBN, which is why old cannabis contains more CBN.
"Delta-9" (Δ9) gives the position of a double bond in the ring. A related compound, delta-8-THC, has the same formula with the double bond in a different place. When people simply say THC, they mean delta-9-THC.
Who discovered THC?
Yehiel Gaoni and Raphael Mechoulam isolated THC from hashish and described its structure in 1964 (Gaoni and Mechoulam 1964). Their work made it possible to study THC as a pure substance. Read the full story in the history of THC.
How does THC work in the body?
THC acts on the endocannabinoid system, a signalling network with two main receptors. CB1 is the main type in the brain and nervous system; CB2 is found mainly in immune tissue (Zou 2018). THC is a partial agonist at both: it switches them on, but not fully, and its effects depend on how many receptors a tissue has (Pertwee 2008). Its action at CB1 in the brain is what causes intoxication. More in the endocannabinoid system explained.
How does THC form in the plant?
Hemp and cannabis don't make much THC directly. They make tetrahydrocannabinolic acid (THCA), which is not intoxicating. Heat from smoking, vaping, baking or processing removes a carboxyl group and turns THCA into THC (Wang 2016). That is why raw plant material and heated material can test so differently. See what is THCA?
THC vs CBD: what is the difference?
THC and CBD share the same atoms, C21H30O2 (PubChem), but they are arranged differently, and that changes how they act.
| THC (delta-9) | CBD | |
|---|---|---|
| Molecular formula | C21H30O2 | C21H30O2 |
| Intoxicating | Yes | No |
| Action at CB1 | Partial agonist (activates the receptor) | Does not activate it; can block other CB1 agonists in lab tests |
| Form in the living plant | THCA | CBDA |
| Legal status | Controlled in most countries | Rules for CBD products vary by country and product type |
Sources for the table: Pertwee 2008, Wang 2016, PubChem. For the full comparison, see CBD vs THC and what is CBD?
What are the effects and risks of THC?
Studies in people describe these acute and long-term effects:
- Memory and attention: in a controlled study, 15 mg of oral THC impaired learning and episodic memory about two hours after the dose, and participants rated themselves "stoned" for up to 8 hours; no effects remained after 24 hours (Curran 2002). A systematic review found verbal learning, memory and attention to be the functions most consistently impaired by both acute and chronic use (Broyd 2016).
- Anxiety and paranoia: anxiety reactions and panic attacks are the acute symptoms most often linked with cannabis (Crippa 2009). In a trial of 121 people prone to paranoid thoughts, intravenous THC increased paranoia (Freeman 2015).
- Psychosis: in a European study, daily cannabis use was linked with about three times the odds of a first psychotic episode compared with never using, rising to nearly five times for daily use of high-potency cannabis (10% THC or more) (Di Forti 2019).
- Dependence: in US survey data, the estimated lifetime probability of becoming dependent was 8.9% for people who had used cannabis (Lopez-Quintero 2011).
Effects vary with the dose, the person and how often they use cannabis.
How long does THC stay in your system?
It depends on how much and how often someone uses cannabis and on the type of test. In regular users, THC metabolites leave the body slowly. In a study of 86 chronic users under supervised abstinence, urine tests stayed positive for an average of 27 days, and some took up to 77 days to fall below the cut-off for good (Ellis 1985). What this means for CBD products is covered in CBD, drug tests and driving.
From our production
We test every batch in Switzerland, and THC is printed to two decimals on the certificate. In our full-spectrum oils, 99.9% of batches measure between 0.12% and 0.17% THC.
— Robin Roy Krigslund-Hansen, co-founder and CEO
Frequently asked questions
What is tetrahydrocannabinol?
Tetrahydrocannabinol (THC) is the main intoxicating compound in cannabis. It acts on CB1 receptors in the brain, which causes the high. It was isolated in 1964 by Gaoni and Mechoulam.
What does THC stand for?
THC stands for tetrahydrocannabinol, usually meaning delta-9-tetrahydrocannabinol. The name means a form of cannabinol (CBN) with four extra hydrogen atoms; delta-9 gives the position of a double bond.
Is THC the same as CBD?
No. They have the same molecular formula, C21H30O2, but a different structure. THC activates the CB1 receptor and is intoxicating; CBD does not activate it and is not intoxicating.
How long does THC stay in your system?
It depends on the dose, how often cannabis is used and the test. In one study of chronic users, urine tests stayed positive for an average of 27 days and up to 77 days in some people.
Is THC addictive?
It can be. In US survey data, about 9% of people who had used cannabis developed dependence at some point.
Related guides
This article is general information about THC and is not medical or legal advice. Formula Swiss does not sell intoxicating cannabis products; our CBD oils are cosmetics for use on the skin. Read our full disclaimer.
Last reviewed:
Sources
- Gaoni Y, Mechoulam R. Isolation, structure, and partial synthesis of an active constituent of hashish. J Am Chem Soc 1964;86(8):1646–1647. doi:10.1021/ja01062a046
- Maioli C et al. Cannabinol: history, syntheses, and biological profile of the greatest "minor" cannabinoid. Plants (Basel) 2022;11(21):2896. doi:10.3390/plants11212896
- National Center for Biotechnology Information. PubChem Compound Summaries: tetrahydrocannabinol (CID 16078), cannabidiol (CID 644019), cannabinol (CID 2543)
- Zou S, Kumar U. Cannabinoid receptors and the endocannabinoid system: signaling and function in the central nervous system. Int J Mol Sci 2018;19(3):833. doi:10.3390/ijms19030833
- Pertwee RG. The diverse CB1 and CB2 receptor pharmacology of three plant cannabinoids: Δ9-tetrahydrocannabinol, cannabidiol and Δ9-tetrahydrocannabivarin. Br J Pharmacol 2008;153(2):199–215. doi:10.1038/sj.bjp.0707442
- Wang M et al. Decarboxylation study of acidic cannabinoids: a novel approach using ultra-high-performance supercritical fluid chromatography/photodiode array-mass spectrometry. Cannabis Cannabinoid Res 2016;1(1):262–271. doi:10.1089/can.2016.0020
- Curran HV et al. Cognitive and subjective dose-response effects of acute oral Δ9-tetrahydrocannabinol (THC) in infrequent cannabis users. Psychopharmacology (Berl) 2002;164(1):61–70. doi:10.1007/s00213-002-1169-0
- Broyd SJ et al. Acute and chronic effects of cannabinoids on human cognition – a systematic review. Biol Psychiatry 2016;79(7):557–567. doi:10.1016/j.biopsych.2015.12.002
- Crippa JA et al. Cannabis and anxiety: a critical review of the evidence. Hum Psychopharmacol 2009;24(7):515–523. doi:10.1002/hup.1048
- Freeman D et al. How cannabis causes paranoia: using the intravenous administration of Δ9-tetrahydrocannabinol (THC) to identify key cognitive mechanisms leading to paranoia. Schizophr Bull 2015;41(2):391–399. doi:10.1093/schbul/sbu098
- Di Forti M et al. The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): a multicentre case-control study. Lancet Psychiatry 2019;6(5):427–436. doi:10.1016/S2215-0366(19)30048-3
- Lopez-Quintero C et al. Probability and predictors of transition from first use to dependence on nicotine, alcohol, cannabis, and cocaine: results of the NESARC. Drug Alcohol Depend 2011;115(1–2):120–130. doi:10.1016/j.drugalcdep.2010.11.004
- Ellis GM Jr et al. Excretion patterns of cannabinoid metabolites after last use in a group of chronic users. Clin Pharmacol Ther 1985;38(5):572–578. doi:10.1038/clpt.1985.226
