King’s College London challenges belief that cannabis with high CBD prevents psychotic experiences

16 Nov 2022 --- Researchers from the Institute of Psychiatry, Psychology & Neuroscience (IoPPN), King’s College London, have challenged the belief that cannabis with higher levels of cannabidiol (CBD) – a compound often taken in supplement form for stress alleviating properties – protects users from psychotic experiences when getting high.

The scientists based this conclusion on experiments that altered the ratio of CBD to delta-9-tetrahydrocannabinol (THC), which is the psychoactive component in cannabis.

The lead author of the study published in Neuropsychopharmacology is a proponent of enforcing a tax on CBD products to curb harmful use. 

“Experience from alcohol regulation shows that taxing products or setting prices based on their strength can reduce harmful use,” Dr. Amir Englund, research fellow at King’s IoPPN tells NutritionInsight.

“One option, for places where cannabis is regulated, would be to tax cannabis products by their THC content, which would discourage people from using the strongest varieties.”

CBD levels hold little impact
THC is the main intoxicating compound of cannabis. CBD is the second most common cannabis compound and is not intoxicating, although it has pharmacological activities. Both compounds can be found in licensed medications.

The same research team had previously found that pre-emptively taking a high dose of CBD in a capsule a few hours before using cannabis may reduce the adverse effects of THC. 

But in this particular study, the scientists found that increasing the dose of CBD did not significantly change the effects of THC on cognitive performance, memory, psychotic symptoms or how pleasurable the drug experience was.

“In our study, we saw that adding CBD to a fixed dose of THC did not change its cognitive, psychological, physiological or subjective effects,” Englund highlights.The IoPPN researchers would like the premise of their research to be taken up by policymakers. 

“This tells us that for people who wish to experience less negative effects of cannabis (memory impairment and psychotic-like effects), it is the THC that needs to be reduced – rather than increasing CBD.” 

Other studies that looked at long-term use have found that cannabis varieties with higher amounts of THC have a higher risk of addiction and mental health problems compared to weaker cannabis varieties. 

The experiment
The researchers explored the effect of altering the CBD:THC ratio in cannabis. Healthy volunteers (N:46) completed a randomized and double-blind trial. Over the course of four experiments, each participant inhaled cannabis vapor containing 10 mg of THC and a differing level of CBD (0 mg, 10 mg, 20 mg or 30 mg). 

“We used one cannabis variety that only had THC and one that only contained CBD from the Dutch company Bedrocan,” Englund outlines.

They combined these varieties to achieve 0:1 (10 mg THC), 1:1 (10 mg CBD, 10 mg THC), 2:1 (20 mg CBD, 10 mg THC) and 3:1 (30 mg CBD, 10 mg THC) CBD:THC ratios.

“None of the CBD levels studied protected our volunteers from the acute negative effects of cannabis, such as anxiety, psychotic symptoms and worse cognitive performance,” says Englund.

The participants completed a series of tasks, questionnaires and interviews designed to measure the effect on their cognitive abilities, the severity of psychotic symptoms and the pleasing effects of the drug.

“It also did not change the quality of the intoxication in any way. The only effect of CBD we saw was that as the concentration of CBD increased, the more the participants coughed. We asked volunteers to listen to a favorite song on each visit and taste a piece of chocolate,” explains Englund. 

Cannabis increased the pleasurability of music and chocolate, but CBD had no enhancement effect. 

Englund continues: “We saw that all of the CBD:THC ratios produced the same level of cognitive impairment – tests of memory performance such as remembering a word list and a series of numbers – and psychotic-like experiences – strange ideas, suspiciousness, hearing/seeing strange things (hallucinations) – suggesting the added CBD is not protective.” 

Avoid the negative effectsThe benefits of taxing products have been proven through alcohol regulation, where higher prices decrease harmful use.
THC and CBD are both produced from the same compound in the cannabis plant, so a variety with higher amounts of CBD will naturally be lower in THC, the researchers note. 

They conclude it may still be safer for users to choose cannabis with higher CBD:THC ratios, but that’s because the same amount of cannabis will contain less THC than a lower CBD:THC variety. 

“Overall, our advice to people wanting to avoid the negative effects of THC is to use less of it,” says Englund.

Professor Philip McGuire, the study’s senior author and former head of the department of psychosis studies at King’s IoPPN, says the findings make an important contribution to the ongoing debate around the risks of cannabis use. 

“While CBD on its own is known to have a number of positive effects in humans, our data suggest that, at the doses typically present in cannabis, it does not protect against the negative effects of THC,” explains McGuire. 

The research paper, Does cannabidiol make cannabis safer? A randomised, double-blind, cross-over trial of cannabis with four different CBD:THC ratios is funded by a research grant from the Medical Research Council. 

Regulations on the horizon
The researchers urge policymakers to continue examining their findings in relation to the medicinal and recreational uses for cannabis.

“I believe that users should be able to make informed decisions about their cannabis use. Therefore, it is essential that we do more research which can provide practical information about the likely effects of different types of cannabis and what the likely effects from a certain dose of THC is,” says Englund. 

There are regulatory complexities surrounding the sale of CBD. However, new research continues to expand the common understanding of its effects and safety.

Daily consumption of oral CBD was recently found to have a “strong safety profile,” in a recent industry-backed study. The findings may help minimize the US Food and Drug Administration’s safety concerns around CBD and pave the way for regulation.

By Inga de Jong