CBL (cannabicyclol) is a minor cannabinoid that forms when CBC (cannabichromene) is exposed to light, so it turns up mainly in aged cannabis. It is a breakdown product, not one the plant makes directly. Research on it is limited to a few laboratory studies, and it has not been tested in people.
Key facts
- Formula
- C21H30O2, the same as THC and CBD, with a different ring structure
- How it forms
- From CBC, by light (photochemical reaction) or acid catalysts
- Amount in cannabis
- Small; more in older or light-exposed material. Detected in 67% of 80 US CBD oils tested
- Cannabinoid receptors
- Weak interaction with CB1 and CB2 in lab tests
- Human studies
- None published (as of October 2026)
What is CBL (cannabicyclol)?
CBL is one of the many minor cannabinoids found in cannabis. It shares its molecular formula, C21H30O2, with THC and CBD, but its atoms are arranged in a different, more compact ring system (PubChem).
A 2016 review of all known phytocannabinoids points out that much of the variety in cannabis comes from non-enzymatic changes. Heat, light and oxygen transform a small set of main cannabinoids, including CBC, into many others. CBL is one of these products (Hanuš et al., 2016).
How does CBL form?
CBL comes from CBC (cannabichromene). In 1968, a team that included Raphael Mechoulam showed that light converts CBC into cannabicyclol (Crombie et al., 1968). Chemists have since used the same conversion to study CBC itself (Agua et al., 2021).
Acids can drive the reaction as well. A 2025 study converted CBC into CBL with several acidic catalysts, with a yield of up to 60% (Haghdoost et al., 2025).
Because light is the main trigger, fresh plant material contains little CBL. Older cannabis, or material stored in the light, contains more. Read more about how heat and storage change cannabinoids.
Does CBL get you high?
There are no human studies to answer this directly. In laboratory binding tests, CBL interacted only weakly with the CB1 and CB2 cannabinoid receptors (Haghdoost et al., 2025). CB1 is the receptor behind the THC high, so a weak interaction makes a THC-like effect unlikely. That remains an inference from lab data, not a tested result.
What does research show about CBL?
Very little, so far. The 2025 study is the first to describe its biological activity in detail. In cell assays, CBL bound strongly to the 5-HT1A serotonin receptor. At high concentrations it acted as a weak agonist there. At low concentrations it boosted the receptor's response to serotonin (Haghdoost et al., 2025).
The authors see this as a lead for drug discovery. It does not show any effect in people. Several of the authors also worked for cannabis companies, which the paper declares.
CBL vs CBC vs CBN: what is the difference?
| Feature | CBL (cannabicyclol) | CBC (cannabichromene) | CBN (cannabinol) |
|---|---|---|---|
| Origin | Formed from CBC by light or acid | Made by the plant (as CBCA) | Formed from THC by oxidation |
| Found in | Aged or light-exposed material | Fresh and dried plant | Aged material |
| CB1 receptor (lab) | Weak interaction | Weak binding | Binds; partly THC-like in mice |
| Human studies | None | Very few | Few |
Sources for the table: Haghdoost et al., 2025; Hanuš et al., 2016; Wiley et al., 2024. More detail in What is CBN?
Why is CBL rarely on a certificate of analysis?
A certificate lists only the cannabinoids the laboratory tested for. If CBL is not on the list, it was not measured, which is not the same as being absent. Because CBL forms from CBC under light, a higher CBL value can point to older or light-exposed material. It is not rare in finished products: a US analysis of 80 over-the-counter CBD oils detected CBL in 67% of them (Johnson et al., 2025). Our guide on how to read a certificate of analysis explains what is usually listed.
Frequently asked questions
What is CBL (cannabicyclol)?
CBL is a minor cannabinoid that forms when CBC (cannabichromene) is exposed to light or acid. It has the same molecular formula as THC and CBD but a different ring structure.
Is CBL psychoactive?
It has not been tested in people. In laboratory tests it interacted only weakly with the CB1 receptor that causes the THC high, which suggests, but does not prove, that it is not intoxicating.
How is CBL made?
In the plant, light slowly converts CBC into CBL. In the lab, chemists make it from CBC using light or acidic catalysts.
What are the effects of CBL?
No effects in people have been studied. In cell assays, CBL bound strongly to the 5-HT1A serotonin receptor, a finding researchers want to explore further.
Is CBL legal in the UK?
CBL is not named in Schedule 2 of the Misuse of Drugs Act 1971. Cannabis itself, THC and other cannabinol derivatives are Class B drugs, so products made from cannabis plant material can still be controlled.
Related guides
This article summarises published research. It is not medical advice. Formula Swiss CBD oils are sold as cosmetics for use on the skin. They are not food supplements or medicines and are not intended to diagnose, treat, cure or prevent any disease.
Last reviewed:
Sources
- Haghdoost M, DePorre Y, Figi M, Young S, Krebs C, Bonn-Miller MO. An unexpected activity of a minor cannabinoid: cannabicyclol (CBL) is a potent positive allosteric modulator of serotonin 5-HT1A receptor. J Nat Prod 2025;88(1):58–66. doi:10.1021/acs.jnatprod.4c00977
- Crombie L, Ponsford R, Shani A, Yagnitinsky B, Mechoulam R. Hashish components. Photochemical production of cannabicyclol from cannabichromene. Tetrahedron Lett 1968;(55):5771–5772. doi:10.1016/s0040-4039(00)76346-5
- Agua AR, Barr PJ, Marlowe CK, Pirrung MC. Cannabichromene racemization and absolute stereochemistry based on a cannabicyclol analog. J Org Chem 2021;86(12):8036–8040. doi:10.1021/acs.joc.1c00451
- Hanuš LO, Meyer SM, Muñoz E, Taglialatela-Scafati O, Appendino G. Phytocannabinoids: a unified critical inventory. Nat Prod Rep 2016;33(12):1357–1392. doi:10.1039/c6np00074f
- Wiley JL, Marusich JA, Blough BE, et al. Evaluation of cannabimimetic effects of selected minor cannabinoids and terpenoids in mice. Prog Neuropsychopharmacol Biol Psychiatry 2024;132:110984. doi:10.1016/j.pnpbp.2024.110984
- Johnson E, Kilgore M, Nuzzo P, Babalonis S. Minor cannabinoid profile of unregulated cannabidiol products. Cannabis Cannabinoid Res 2025;10(2):220–227. doi:10.1089/can.2024.0058
- PubChem. Cannabicyclol (CID 59444380). National Library of Medicine
- Misuse of Drugs Act 1971, Schedule 2. legislation.gov.uk
