CBD enhances the effects of THC instead of mitigating them, new cannabis study reveals

A study published in Clinical Pharmacology & Therapeutics has brought a new perspective on the interaction between cannabidiol (CBD) and tetrahydrocannabinol (THC). The research reveals that, contrary to popular belief, CBD does not reduce the adverse effects of THC, but can intensify them, especially at high doses. The study, led by Geert Jan Groeneveld, a professor of clinical neuropharmacology at Leiden University Medical Center and CEO of the Centre for Human Drug Research, suggests that high doses of CBD (450 mg) significantly increase the effects of THC, likely due to a pharmacokinetic interaction that raises THC levels in the bloodstream.

The therapeutic importance of cannabis

Cannabis has gained prominence both as a recreational drug and for its potential therapeutic uses, especially in pain management. THC, the main psychoactive compound in the plant, is widely recognized for its analgesic properties, but also for causing adverse effects such as cognitive impairment, anxiety, and psychomotor alterations. On the other hand, CBD is non-intoxicating and has been widely touted as capable of attenuating these negative effects of THC. This belief has driven the use of CBD-rich products in both recreational and medicinal fields.

However, the scientific evidence supporting the idea that CBD can neutralize the adverse effects of THC remains inconsistent. While some studies indicate that CBD may reduce THC-induced anxiety and psychosis, others have not found clear evidence of these protective effects.

Demystifying the interaction between CBD and THC

In an interview with the PsyPost, Groeneveld commented that "people involved in the cannabis field have always said that CBD softens the effects of THC, reduces anxiety, and creates an 'entourage effect' with other cannabinoids, but the scientific evidence was weak. As pharmacologists, we know how to scientifically demonstrate drug interactions, so we conducted a rigorous experiment" .

To better clarify this issue, Groeneveld and his team designed a study to test the hypothesis that CBD could mitigate the adverse effects of THC without interfering with its analgesic properties. The goal was to provide more precise guidance on the safe and effective use of cannabis-based products.

Study methodology

The research was conducted with 37 healthy volunteers, aged 18 to 45, who had previous experience with cannabis but were not frequent users. They needed to meet strict health criteria, including being free of psychotic disorders and conditions that could influence pain sensitivity. Volunteers were also instructed to abstain from cannabis and other substances for a few weeks before the experiment to avoid any interference with the results.

The study, conducted at the Centre for Human Drug Research in the Netherlands, used a double-blind, placebo-controlled, five-way crossover experimental design. This means that each participant received five different treatments in random order, with sufficient intervals between sessions to eliminate possible residual effects from previous treatments. The treatments included THC alone, THC combined with three different doses of CBD (10 mg, 30 mg, and 450 mg), as well as a placebo.

The surprising results

Volunteers received the CBD doses 30 minutes before THC to ensure that both substances peaked in the bloodstream simultaneously. Over six hours, subjective reactions such as mood, anxiety, and feeling 'high' were measured, along with objective tests evaluating cognitive and psychomotor performance, such as reaction times and postural stability. Pain tests were also conducted, assessing the analgesic effects of the substances with thermal, pressure, and cold stimuli.

Contrary to popular belief, researchers found that the highest dose of CBD (450 mg) significantly increased the effects of THC. Participants reported a greater sense of intoxication and showed poorer performance in cognitive and psychomotor tests. According to Groeneveld, this likely occurred due to CBD's interference with THC metabolism, leading to higher THC concentrations in the blood.

The lower CBD doses (10 mg and 30 mg) did not alter the effects of THC or mitigate anxiety, cognitive impairment, or other adverse effects. This suggests that CBD does not neutralize the effects of THC when administered orally.

Despite amplifying the psychoactive effects of THC, high doses of CBD did not influence the analgesic properties of THC. This finding indicates that CBD may alter the subjective experience of THC but without enhancing its pain relief potential.

Limitations and future research

Although the study was rigorously controlled, it is not without limitations. One of them is the route of administration: the results apply only to oral ingestion of THC and CBD. As other consumption methods, such as inhalation, affect metabolism differently, the results may not be applicable to other forms of cannabis use. Additionally, the study did not include a CBD-only condition, which would have allowed for a more detailed analysis of the effects of cannabidiol alone.

Nevertheless, Groeneveld states that new studies are being conducted, focusing solely on the use of high doses of CBD. “We continue to conduct a study solely with CBD, also with very high dosage levels, to try to demonstrate its effects on the central nervous system and brain function. Although we have not yet published, we can already state that there is no evidence that CBD is active in the central nervous system” .

Conclusion

The study published by Groeneveld and his team provides valuable insights into the interaction between CBD and THC, challenging one of the most widespread beliefs about the use of these compounds. The article “Cannabidiol enhances the psychotropic effects and plasma concentrations of Δ9-tetrahydrocannabinol without improving its analgesic properties” concludes that CBD does not mitigate the adverse effects of THC and, at high doses, may even increase them .