CBN: What It Is, Effects and Safety | PatientsCann UK

CBN

cannabinol

pronounced: kan-uh-bih-NOL

The ageing cannabinoid - forms as THC gets old, often linked with sleep.

Neutral cannabinoidFormula: C21H26O2Intoxicating: Mild
Type
Neutral
Formula
C21H26O2
Intoxicating
Mild
Key focus
Sleep

Cannabinol · 310.4 g/mol

The molecule

Chemical structure

This is the accurate skeletal structure of CBN, drawn from PubChem data. Each corner and line-end is a carbon atom, and the red O marks oxygen. Its formula is C21H26O2 and it weighs 310.4 g/mol.

SleepMildly relaxingPain reliefAnti-inflammatory

About

What is CBN?

Cannabinol, or CBN, is the cannabinoid of old cannabis. The plant does not really set out to make it. Instead, it forms slowly when THC is left exposed to air, heat and light. Older, or poorly stored, cannabis tends to have more CBN.

CBN is only very mildly intoxicating, far weaker than THC. It is best known for its reputation as a sleep aid, although the science behind that is thinner than the marketing suggests.

In the body

How CBN Works

CBN is a weak activator of the CB1 receptor, roughly one-tenth as strong as THC, which is why it barely makes you high. It binds the CB2 receptor a little more strongly, linking it to the immune system.

Its popular link with sleep may come partly from the other sedating compounds found in aged cannabis, rather than from CBN alone. Good-quality human studies on CBN for sleep are still needed.

Receptor snapshot

Where CBN Acts

The endocannabinoid system has two main receptors. Here is how strongly CBN acts on each.

CB1Brain & nervous system
Weak / indirect

Weak CB1 activity - about one-tenth as strong as THC, so only very mildly intoxicating.

CB2Immune system & body
Partial

Binds CB2 a little more strongly than CB1.

In the plant

How CBN is Made

Unlike most cannabinoids, CBN does not come straight from CBGA. It is a breakdown product: THC slowly turns into CBN as it oxidises over time.

This is why fresh cannabis has very little CBN, and why the amount rises the longer a product is stored.

Comes fromDelta-9-THC→ over time →CBN

Good to know

Safety and Side Effects

There is not much safety research on CBN by itself. Because it is mildly intoxicating, it could in theory add to the effects of THC. Few side effects have been reported, but this reflects how little it has been studied rather than proof that it is risk-free.

Speak to your prescriber before using a CBN product for sleep, especially alongside other sleep medicines.

Questions

CBN: Common Questions

Does CBN help you sleep?
CBN is often sold as a sleep aid, but the research is limited. Some of its reputation may come from other compounds in aged cannabis rather than CBN itself. Speak to your prescriber before using it for sleep.
Where does CBN come from?
CBN is not made directly by the plant. It forms slowly when THC is exposed to air, heat and light over time, which is why older cannabis tends to have more of it.
Back to full Cannabinoids Guide
Important: This page is for education only. It is not medical advice. Cannabinoid research is still developing, and many studies have been done in cells or animals rather than people. Always speak to your prescriber before changing your treatment. PatientsCann UK does not recommend any specific cannabis product.

References

  1. ElSohly, M.A. and Gul, W. (2014) 'Constituents of Cannabis sativa', in Pertwee, R. (ed.) Handbook of Cannabis. Oxford: Oxford University Press, pp. 3-22.
  2. Morales, P., Hurst, D.P. and Reggio, P.H. (2017) 'Molecular targets of the phytocannabinoids: a complex picture', Progress in the Chemistry of Organic Natural Products, 103, pp. 103-131. doi: 10.1007/978-3-319-45541-9_4.
  3. Russo, E.B. (2011) 'Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects', British Journal of Pharmacology, 163(7), pp. 1344-1364. doi: 10.1111/j.1476-5381.2011.01238.x.
  4. National Center for Biotechnology Information (2025) PubChem Compound Database. Bethesda: U.S. National Library of Medicine. Available at: https://pubchem.ncbi.nlm.nih.gov (Accessed: 29 July 2026).