CBD content has no bearing on cannabis safety 

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The CBD content of cannabis has no effect on the drug’s safety, according to researchers from the Institute of Psychiatry, Psychology & Neuroscience at King’s College London. 

The researcher’s findings challenge the widely held belief that higher CBD content in cannabis protects the user from psychotic experiences and memory problems. The research team have urged policymakers to consider their findings when exploring the subject of cannabis for both medicinal and recreational use.  

The researchers invited 46 healthy volunteers to take part in a randomised and double-blind trial. In the trial, each participant inhaled cannabis vapour containing 10mg of THC with differing CBD content (0mg, 10mg, 20mg, or 30mg). The participants were then required to complete a series of tasks, questionnaires and interviews designed to measure the effects of cannabis on their cognitive abilities. The researchers also wanted to measure the severity of any psychotic symptoms and how pleasurable the users found the drug.   

The effects of CBD on THC

The King’s College research team had previously found that pre-emptively taking a high dose of CDB before using cannabis may reduce some of the adverse effects of THC, which is the psychoactive component of the drug.  

In the current study, the researchers examined the effect of altering the CBD:THC ratio in cannabis. They found that increasing the dose of CBD did not have any significant change on the THC’s effect on cognitive performance, psychotic symptoms or how pleasurable the drug experience was. 

“None of the CBD content levels studied protected our volunteers from the acute negative effects of cannabis, such as anxiety, psychotic symptoms, and worse cognitive performance. It also did not change the quality of the intoxication in any way,” said Dr Amir Englund, a research fellow at King’s College and the study’s lead author. 

“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 favourite song on each visit and taste a piece of chocolate. Although cannabis increased the pleasurability of music and chocolate compared to when volunteers were sober, CBD had no impact,” added Englund.  

THC and CBD are both produced from the same compound in the cannabis plant, this means varieties that produce a higher amount of CBD will naturally be lower in THC. The researchers recommend that it may be safer for users to choose cannabis with CBD:THC ratio, but that is because the same amount of cannabis will contain a lower CBD:THC variety. Overall, the researchers advise people who are wanting to avoid the negative effects of THC to use less of it.  

Higher CBD content will not reduce the negative effects of THC

“These 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 that are typically present in cannabis, it does not protect against the negative effects of THC,” said Professor Philip McGuire, the study’s senior author and former Head of the Department of Psychosis Studies at King’s College.  

“These challenges the commonly held view by many cannabis users that cannabis with a higher CBD content provides a buffer against the adverse effects of cannabis,” he concluded.  


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