CBL: The (almost) forgotten cannabinoid

For decades, the discussion about cannabis has focused on THC, the central, psychoactive component of the cannabis plant. In recent years, interest has fortunately broadened - now CBD (cannabidiol) is increasingly being discussed and researched.

But did you know that there are many more cannabinoids, each with very different properties and effects? Especially the so-called "minor cannabinoids," those that occur only in small amounts in the cannabis plant, are increasingly coming into focus.

The latest studies are focusing on a little-researched cannabinoid: cannabicyclol (CBL). This article explains what we know about CBL, what effects current studies suggest are possible, and what the legal situation is currently like in Germany and internationally.

Cannabicyclol (CBL) is a naturally occurring component of the cannabis plant, a so-called cannabinoid. Because CBL is only present in very small amounts in cannabis (around 0.5% depending on the strain, while THC and CBD range between 10 and 25%) and is not psychoactive, it was largely ignored for a long time.

CBL was first discovered in 1964. It is formed by the degradation of cannabichromene (CBC), another "minor cannabinoid", e.g. by light and oxygen. The degradation of CBC happens either over time due to the influence of light or through oxygen (oxidation) and heat on the cannabis plant. The age of the plant therefore plays a role in how much CBL is ultimately contained in the cannabis.

A characteristic feature is that CBL has no intoxicating effect and is not psychoactive. In contrast to THC and other cannabinoids (e.g. HHC), CBL does not alter consciousness, it does not make you "high" and is therefore more similar to CBD.

Although CBL was discovered in the 1960s, a comprehensive pharmacological evaluation is still pending. Neither the risks and side effects of CBL nor its medical potential have been fully described to date. However, this seems to be changing.

A current study on CBL was published in early 2025 and for the first time dealt in detail with the biological effectiveness of CBL. (1) This was also due to the fact that a method had been found for the first time to produce CBL from CBC in a controlled manner - and thus to obtain a sufficient quantity for various experiments.

CBL showed the following properties, which also make it interesting for medical applications: In high concentrations, CBL acts weakly as an agonist, meaning it can itself act on the receptors of the endocannabinoid system. The prerequisite is that enough CBL is present. Researchers assume that such a high concentration does not occur naturally in the plant, meaning CBL would have to be produced in the laboratory.

What is much more interesting, however, is that even in very low concentrations, cannabicyclol acts as a "positive allosteric modulator" (PAM) for the serotonin receptor 5-HT1A. CBL itself does not act like serotonin, but it can enhance the effect of serotonin and the substances it is supposed to simulate (e.g. medications like benzodiazepines). These are used, among other things, for muscle spasms, sleep problems, and anxiety disorders.

It could therefore be that CBL could have comparable effects to CBD, including relaxing, anti-inflammatory and antioxidant properties. Therapeutic applications of CBL could also arise for depression and anxiety. Even in neurodegenerative diseases such as Alzheimer's, the 5-HT1A receptor has been shown to play a role. (2)

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Overall, our perception of minor cannabinoids is currently changing. Previously, it was assumed that they played hardly any role compared to other cannabinoids and were therefore pharmacologically negligible. This is slowly changing.

With the new interest in minor cannabinoids, a very special phenomenon is once again coming into focus: the so-called entourage effect. It states that cannabinoids can be particularly effective in combination with other cannabinoids - or that the rather unpleasant effects (e.g. from THC) can be mitigated by other cannabinoids.

This modulating effect is already known from CBD: cannabidiol mitigates the psychoactive effect of THC and brings the pain-relieving and anti-inflammatory properties more into the foreground. (3) This is, of course, particularly relevant for medical applications of THC where one would rather not experience a high. The entourage effect is probably also the reason why natural flowers or full-spectrum oils are gentler and at the same time more effective than synthetic cannabinoids.

Although there is still a lack of research here, it can be assumed that CBL, as a non-psychoactive cannabinoid, also has such a modulating effect on the psychoactive components of hemp.

Even though the latest research on CBL has yielded very interesting results, it is not yet time to celebrate CBL as a new miracle cure. So far, all we know is that CBL can influence the effects of other cannabinoids like THC – what side effects it might have itself is not yet clear.

It is also far from clear what concentrations are actually needed to achieve the effects observed so far only in cell experiments (in vitro) in the human body. We also do not yet know how stable CBL is (e.g., against light and oxidation), what its actual bioavailability is like, and how the substance is metabolized.

Without clinical studies in humans, we know nothing about what dose of CBL would be useful, what dosage form is needed, etc. It also needs to be clarified whether the modulation of the 5-HT1A receptor by CBL alone is sufficient, for example, to relieve inflammation, or whether combinations with other substances are necessary.

UN agreements on the control of narcotic drugs and psychotropic substances distinguish between whether a substance has psychoactive or intoxicating effects and whether it has a high potential for abuse. While the "Convention on Psychotropic Substances" has listed substances that can alter consciousness, mood, or perception since the 1970s, the "Single Convention on Narcotic Drugs" of 1961 regulates which substances are treated as drugs for tax or control purposes.

CBL is not yet listed in either convention. One could say that cannabicyclol (CBL) has been forgotten by the UN - which is certainly due to its very low concentration and the lack of research to date, but also to the fact that CBL has no psychoactive effect.

In Germany, the Narcotics Act (BtMG) governs which substances are prohibited or subject to control, especially those with psychoactive effects or a high risk of abuse. The decisive factors here are the provisions of international agreements, scientific assessments, risk of abuse, effect profile, etc.

Because CBL is not psychoactive, it does not appear in the BtMG. Similar to the UN, German law distinguishes between material effects (e.g., intoxicating) and chemical structural characteristics. A substance is not automatically prohibited solely based on its origin from cannabis if it has no psychoactive effects and the potential for abuse is considered low.

It is therefore unlikely that CBL will ever be added to the list of prohibited or regulated compounds.

What could change with increasing interest in CBL is its use as a medicine, which in turn would entail its own regulatory requirements. If CBL – similar to CBD – is used in higher concentrations in the future (e.g., as a food supplement), it could be included in the EU's Novel Food regulation. However, this is currently still pure speculation.

CBL is a good example of how much is still unclear in cannabinoid research. For decades, it was considered merely a breakdown product of CBC, without its own pharmacological potential. However, recent research shows that due to its influence on the 5-HT1A receptor, CBL could play an interesting role in medicine in the future - be it in the treatment of anxiety disorders, depression, or other diseases in which serotonin plays a central role.

Nevertheless, CBL will certainly not become the big player in the world of cannabinoids - that will probably remain the two giants THC and CBD. But: CBL in combination with other cannabinoids will certainly become a topic that we will hear more about.

Legally, the situation remains clear: Because CBL has no psychoactive effect and no recognizable potential for abuse, it is not regulated in international agreements or in the German BtMG. This clearly distinguishes it from THC or synthetic cannabinoids. Should CBL prove to be medically significant in the future, its regulation will likely occur through pharmaceutical or food law, not through narcotics law.

Medical disclaimer