Does CBD diminish the effect of THC?

Analysis of the components of the cannabis plant

Cannabis is a plant that contains a variety of chemical compounds, including cannabinoids, the best known of which are tetrahydrocannabinol (THC) and cannabidiol (CBD). THC is responsible for the psychotropic effects associated with marijuana use, while CBD has gained popularity for offering therapeutic benefits without producing psychotropic effects.

There is a growing interest in the interaction between both compounds, as pointed out by some scientific studies. Today on the Cannactiva blog, researcher Alberto Sainz Cort, author of scientific studies on the interactions between CBD and THC, explains the effect of THC and CBD when consumed together.

THC and CBD: What are they and how do they work?

THC is the most abundant cannabinoid in the marijuana plant and the main responsible for the psychotropic effects derived from cannabis consumption, characterized by feelings of euphoria, relaxation, altered mental perception and other neuropsychological effects.

CBD is the second most abundant cannabinoid in the cannabis plant, but its effects are different from those of THC. Several studies have shown that it does not produce psychotropic effects like THC. However, cannabidiol exerts other effects on the body with therapeutic potential, such as the relief of chronic pain, anxiety, psychotic disorders or insomnia. We discussed this topic in depth in the post on the differences between THC and CBD.

In addition to the effects produced by each cannabinoid separately, it has been observed that, when consumed together, CBD can modulate the effects of THC, which could influence the intensity of these effects and the consumer’s experience.

Combination of CBD and THC: Diminution or potentiation of effects?

Some cannabis users realized some time ago that cannabis strains that had relatively high percentages of CBD (in addition to THC) were not as potent as other strains that had only THC.

In fact, the classic Moroccan hashish of a decade or two ago did not get as high as marijuana, despite having very similar amounts of THC to marijuana. However, hashish did contain other cannabinoids such as CBD or cannabinol (CBN), whereas, in general, the marijuana flowers available at that time contained only THC, with percentages of other cannabinoids below 1%.

Some claimed that CBD reduced the effects of THC or made the high more bearable, but no one had scientific or clinical proof of this, and the evidence was essentially based on the experiences of smokers.

In addition, it was difficult to find cannabis products with balanced ratios of CBD and THC until Resin Seeds or GW Pharmaceuticals marketed Cannatonic and Sativex (THC:CBD 1:1) seeds, respectively, during the first decade of the 2000s.

Scientists had been studying the effects of CBD for some time, but very few had considered the study of combining CBD with THC, with a few exceptions, including the studies of Ethan Russo (1,2), who had collaborated in the creation of Sativex.

Possible applications in medical cannabis

Research on CBD (without THC) was demonstrating antipsychotic properties (3-5), which could already hint at its effects in conjunction with THC because THC was already known at that time to produce psychotic effects (6-9).

When high-CBD strains finally became commercially available (following Charlotte’s childhood epilepsy case), doctors and medical cannabis patients realized that CBD could make the effect of THC more bearable when used therapeutically.

It should be noted that many patients who use cannabis medicinally do not want to get high, and, in fact, consider the high to be an adverse effect of the medication. Therefore, the study of THC interactions with CBD (and other compounds) began to take on more importance.

Interactions between THC and CBD

Interaction mechanisms

Cannabinoids act on the endocannabinoid system, which is responsible for various cellular mechanisms and is distributed throughout the body.

Basically, the classic effects of marijuana are produced by the psychotropic properties of THC. THC binds to cannabinoid receptors in the brain (mainly the CB1 receptor), which are distributed in several areas of the central nervous system, producing its characteristic “high” effects.

CBD does not get high, probably because of the way it interacts with the CB1 receptor. In fact, CBD is a negative allosteric modulator of the CB1 receptor (10). This means that their binding does not activate the receptor, but rather negatively modulates its activity. Thus, CBD could modulate the effects of THC on the CB1 receptor, which would result in a decrease of its psychotropic effects. However, it is possible that the modulatory effects of CBD on THC are also due to interactions with other brain receptors, such as serotonergic receptors (11).

What are the benefits of strains with balanced THC/CBD ratios for the cannabis consumer?

There are indications that cannabis strains with balanced THC to CBD ratios provide a more bearable experience for the consumer, as CBD has the potential to mitigate some of the psychotropic effects of THC. This may result in a reduction of psychotropic and psychotic effects associated with THC consumption, such as anxiety or paranoia, and in medical cannabis users, enhance combined therapeutic benefits of both cannabinoids.

Scientific studies on the influence of CBD on the effect of THC

Several scientific studies have addressed the interaction between THC and CBD, focusing on the subjective effects described by individuals when they receive co-administration, either orally or inhaled, of both cannabinoids.

I will start by mentioning one of those studies, which I designed and executed together with the ICEERS foundation a few years ago in a cannabis club in Barcelona.

Study at the Barcelona Cannabis Club

Our study (12), published in the Journal of Clinical Psychopharmacology, was developed as naturalistic research but maintaining a clinical trial-like control, randomized, dose-standardized, placebo-controlled and double-blinded.

Taking into account that THC produces psychotic effects and that these are highly influenced by the environment around us, it was most appropriate to carry out the study in a cannabis club in Barcelona. As many of you know, a cannabis club is a private venue where members gather to obtain and consume cannabis. It is therefore a place that is familiar to users and where they feel at ease, as well as representing a real and common situation of cannabis use. If the study were conducted in a hospital or a laboratory, the context could make the participants uncomfortable, which could greatly affect the psychological variables we want to measure. Because, after all, the subjective effects of cannabis are psychological effects (like the psychotic effects produced by THC).

For the study, we invited members of the Strain Hunters cannabis club to try four different dispensary products: an extract with 65mg THC, another with 130mg CBD, a combination of 65mg THC + 130mg CBD, and a placebo with no cannabinoids. The tests were conducted in four different sessions.

PAX vaporization device.
PAX vaporization device.

The results showed that the combination of THC and CBD (1:2 ratio) decreased the subjective effects of THC, especially the feeling of “being high”, and also reduced some of its psychotic effects.

Divergences in Research on the CBD-THC Interaction

In one of the most important scientific reviews on the subject, (13) researchers found that some studies support the hypothesis that CBD can counteract the subjective effects of THC, but others find the opposite. This may be due to differences in routes of administration, dosages and CBD:THC ratios. For example, in another study (14) they used a CBD (8 mg): THC (16 mg) ratio of 2:1 in their study and found no reduction in THC effects on any of the scales when vaporized together with CBD. Another study (15) found increased subjective and psychotic effects when participants vaporized a CBD (4 mg): THC (8 mg) ratio of 1:2 compared to THC alone (8 mg), whereas they found reduced subjective and psychotic effects with a CBD (400 mg): THC (8 mg) ratio of 50:1 compared to THC (8 mg).

In studies using other methods, some found a reduction in THC effects when combined with CBD (16,17) while others did not (18-20).

CBD and its Modulatory Role in the Effects of THC in Regular Cannabis Users

Despite the aforementioned discrepancies, the potential of CBD to reduce the effects of THC has also been demonstrated in other research paradigms, supporting the effects of CBD over THC and explaining some of the psychobiological mechanisms behind it.

In one study (21) they found that daily oral administration of CBD (200 mg) for 10 weeks improved psychological and cognitive symptoms in regular cannabis users without producing side effects. According to this study, CBD would not only help reduce the acute symptoms of THC, but would also reduce the long-term effects of cannabis use, such as depressive and psychotic symptoms and cognitive improvements, including memory improvement.

Another study testing the effects of cannabinoids on resting state networks found that resting state networks were altered by vaporized THC (8 mg), whereas vaporized coadministration of CBD (10 mg) was able to reverse the effects of THC (22). In addition, animal studies also demonstrate CBD-THC interaction explaining possible mechanisms of action (23,24).

Critical analysis of one of the latest published studies

In May 2023, a study by researchers at King’s College London was published in which 46 healthy participants with little or no previous experience of cannabis use were recruited (25). In the double-blind, randomized study, these participants received different cannabis preparations with 10 mg THC and different amounts of CBD (0, 10, 20 and 30 mg) through a vaporizer.

The findings showed that CBD did not attenuate the acute adverse effects of THC, and there were no significant differences between the different ratios of CBD:THC. However, the study has some limitations that could explain the results obtained.

On the one hand, the study does not use any placebo and all products vaporized contain THC. Therefore, the study should not rule out that the effects felt by the participants are due to other causes, including the placebo effect. Another limitation of the study is the methodology of one of the tests to which the participants were subjected. In this test, participants had to leave the hospital room to buy food from a vending machine and return, while under the effects of THC. As we mentioned before, measuring psychological variables in environments that can generate stress, anxiety or paranoia can alter the measurements that are the object of the study. If, in addition to having a participant placed in a hospital surrounded by patients and doctors, he or she is asked to leave the room to shop and return, it is likely to further increase stress, anxiety and paranoia levels.

Undoubtedly, this study must be added to the body of evidence on the interactions of CBD and THC, but taking into account the limitations we have discussed, we cannot conclude that CBD is not able to reduce the effects of THC.

Responsible use and conclusions

Several studies support the idea that CBD can counteract the subjective effects of THC. However, there are other studies that do not support it, and one of the reasons for the discrepancies between studies is that the methodology, variables measured, routes of administration, types of cannabis products used and their concentrations are different for each study. Therefore, the effect of CBD on THC could depend on the CBD:THC ratio, the dose and the route of administration.

Medical cannabis patients and recreational cannabis users can benefit from the effects of CBD’s interaction with THC by attenuating the psychotropic effects of THC, but will need to take into account all the factors we have mentioned to achieve these effects. Generally, the safest way would be to start with low doses of THC and high doses of CBD and adjust depending on the effects you are looking for.

Entourage effect of cannabis

Of course, it should not be forgotten that other cannabinoids and terpenes can also modulate the effects of cannabis, so the more information you have about the characteristics of the cannabis you consume, the easier it is to predict its effects. It should be clarified that the interaction between THC and CBD refers to how these two cannabinoids affect each other, while the entourage effect of cannabis involves the synergy of all cannabis compounds acting together, including the different cannabinoids, terpenes and flavonoids.

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