CBD vs CBN: one comes from the plant, one from aged THC

CBD and CBN are both cannabinoids, compounds specific to hemp, and they have little else in common.

Hemp starts by building CBGA, the shared molecule from which the other cannabinoids derive. An enzyme called CBDA synthase converts it into CBDA, the acidic form of CBD. Heat from drying, burning or extraction then removes a carboxyl group, turning CBDA into CBD. Our article on CBG follows this chain step by step.

CBN forms another way. According to a 2021 review in Frontiers in Pharmacology, it was isolated from Indian hemp as early as 1896 and was the first cannabinoid ever identified. The review adds that ultraviolet light and heat slowly convert THC into CBN, even when storage conditions are good. In the plant, THCA goes down the same path and yields CBNA, the acidic form of CBN.

CBN is a product of ageing, and it can only form from THC. A hemp variety low in THC cannot produce much CBN.

The reference measurement goes back to 1997. Two researchers at the University of Mississippi followed cannabis stored in closed drums, in the dark, at 20 to 22 °C for four years, then published their results in the United Nations Bulletin on Narcotics. On average, THC lost 16.6% of its starting value after one year, 26.8% after two, 34.5% after three and 41.4% after four. The CBN-to-THC ratio rose over time, enough to serve as an estimate of a sample's age.

CBD holds up better. A study from the same university, published in August 2026 in Cannabis and Cannabinoid Research, compared flowers, extracts, oils and isolates kept at room temperature, in a fridge and in a freezer. The study abstract reports that products containing only CBD remained stable at room temperature. Under the same conditions, the THC in THC-rich materials broke down into CBN.

Consider a CBD flower at 0.2% THC kept for four years under the 1997 conditions. It would lose about 41% of its THC, which is 0.08 percentage points. Even if every bit of that THC turned into CBN, and it does not, the flower would contain 0.08% CBN at most. A product sold as "CBN-rich" cannot come from an aged CBD flower. It relies on a different raw material or on a laboratory conversion, and the 2021 review lists semi-synthesis among the ways minor cannabinoids are produced.

The body has two main cannabinoid receptors. CB1, found mostly in the brain, carries the psychoactive effect of THC. CB2 is found mostly on immune cells.

CBD binds poorly to both. According to a 2008 review in the British Journal of Pharmacology, it only displaces a reference ligand from CB1 and CB2 receptors at micromolar concentrations, which means its affinity is low. The effects studied so far involve other targets.

CBN binds better than CBD and less well than THC. The 2021 review describes it as less potent than THC at CB1 and equally potent at CB2. It also notes that clinical studies have not shown any minor cannabinoid to be psychoactive. These receptors are presented on our page about the endocannabinoid system.

Human data on CBN are still thin. A randomised trial published in 2024 gave 293 adults 20 mg of CBN for seven nights, either alone or with 10, 20 or 100 mg of CBD. It missed its primary endpoint, sleep quality, and adding CBD did no better than CBN alone. Our article on CBN in France discusses this trial and the one that followed. No medicine based on CBN is authorised, while the only authorised CBD medicine is Epidyolex.

Neither molecule is a narcotic. The ANSM classified H4CBD, THCP and other derivatives from 3 June 2024, and it expressly excluded CBN and CBNA from that decision. THCA remains permitted in hemp whose THC content does not exceed 0.3%.

Products still have to fit the hemp framework. Under the decree of 30 December 2021, cultivation and trade are limited to varieties listed in the official catalogues with no more than 0.30% Δ⁹-THC, and extracts are capped at the same level. On 29 December 2022, the Conseil d'État struck down the ban on selling raw flowers.

The real restriction concerns what you swallow. On 20 May 2026, the Ministry of Agriculture declared foods containing CBD or other extracted cannabinoids illegal, including food supplements, since none has been authorised under the EU novel food regulation. That covers any CBD + CBN oil or gummy meant to be swallowed. Our overview of CBD regulation in 2026 describes the system. Our article on CBN + THC gummies explains why that combination also comes under narcotics law.

On a certificate of analysis, each cannabinoid appears as a percentage of mass for a flower or a resin and in mg/ml for an oil. Comparing CBD and CBN takes four lines.

1. CBD and CBDA: total CBD is CBD + 0.877 × CBDA, since CBDA loses about 12% of its mass on becoming CBD.
2. CBN: a CBD flower contains only traces, for the reason calculated above, and a rising CBN/THC ratio suggests an old or badly stored flower.
3. Δ⁹-THC and THCA: Δ⁹-THC must be 0.30% or less, and THCA becomes THC when heated.
4. Batch number: it has to match the product.

Every section is covered in our guide to reading a certificate of analysis, and the laboratory page describes the measurement methods. If you want your CBD flowers to form as little CBN as possible, our article on storage gives the light and temperature conditions to aim for.