# CBN

> CBN (cannabinol) is a cannabinoid formed mainly when THC or THCA oxidises after harvest, so high CBN readings usually signal age, heat, light or air exposure, not plant ripeness.

- Canonical: https://genetixbay.com/knowledge/glossary/cbn.html
- Also written: cannabinol, CBNA, cannabinolic acid
- Glossary category: Cannabinoids and terpenes · Evidence: Supported
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

CBN, cannabinol, is a [cannabinoid](https://genetixbay.com/knowledge/glossary/cannabinoid.md) that the plant does not make by enzyme. It forms mainly when [THC](https://genetixbay.com/knowledge/glossary/thc.md) (or [THCA](https://genetixbay.com/knowledge/glossary/thca.md), which yields CBNA) oxidises and aromatises, a reaction driven by oxygen, heat, light and time. That is why CBN is the classic marker of old or poorly stored cannabis and of old [hashish](https://genetixbay.com/knowledge/glossary/hashish.md).

## In practice

Fresh, well-cured flower usually shows CBN under 0.2% w/w or not detected. Material stored warm, in light or with lots of air for months shows rising CBN and falling THC. A high CBN line on a [COA](https://genetixbay.com/knowledge/glossary/coa.md) is a storage story, not a cultivar trait.

## Don't confuse with

- **CBD**: unrelated in origin; CBN comes from THC.
- **Amber trichomes**: a visual change in the head, not a measurement of CBN.

## Myth check

House position: the idea that letting [trichomes](https://genetixbay.com/knowledge/glossary/trichome.md) go amber on the plant fills the bud with CBN and produces "couch-lock" is unsupported. CBN is mainly a post-harvest oxidation product; amber colour on the plant does not mean meaningful CBN. [Harvest timing](https://genetixbay.com/knowledge/glossary/harvest-window.md) is a matter of preference: a few clear, mostly cloudy, some amber. See [trichome ripeness](https://genetixbay.com/knowledge/harvest-cure/trichome-ripeness.md) and [Mythbusters](https://genetixbay.com/knowledge/mythbusters.md).

## Related terms

[THC](https://genetixbay.com/knowledge/glossary/thc.md), [THCA](https://genetixbay.com/knowledge/glossary/thca.md), [Decarboxylation](https://genetixbay.com/knowledge/glossary/decarboxylation.md), [CBL](https://genetixbay.com/knowledge/glossary/cbl.md), [Cannabinoid](https://genetixbay.com/knowledge/glossary/cannabinoid.md)

## Read more

- [Long-term storage: keeping cured flower potent and aromatic](https://genetixbay.com/knowledge/harvest-cure/long-term-storage.md)
- [Trichome ripeness: clear, cloudy, amber, and what the evidence says](https://genetixbay.com/knowledge/harvest-cure/trichome-ripeness.md)

## Sources

1. ElSohly MA, Slade D. 2005. Chemical constituents of marijuana: the complex mixture of natural cannabinoids. Life Sciences 78(5):539-548.
2. Hanuš LO, Meyer SM, Muñoz E, Taglialatela-Scafati O, Appendino G. 2016. Phytocannabinoids: a unified critical inventory. Natural Product Reports 33(12):1357-1392.