Stoned for science: Volunteers smoked cannabis vaporiser for study that could help prevent psychosis

Staff Reporter (25 July, 2019)

'Is there a CBD/THC ratio that’s less harmful?'


Volunteers have been smoking cannabis at King’s College Hospital for the last year and a half for scientific research into preventing drug-induced psychosis, writes Josh Mellor…

The study is trying to find out what the best balance of THC, which gets users high, to CBD, which has no intoxicating effect.

Both substances are found naturally in cannabis, but stronger versions of the drug – such as high potency cannabis, aka ‘skunk’ – are grown to contain much more THC and very little CBD.

It is hoped that by balancing one against the other, the risk of drug-induced psychosis in users could be reduced.

The volunteers were given a dose of THC and CBD cannabis from a ‘Volcano’ vaporisation device before undergoing tests to see how CBD affects their memory performance and mood, as well as subjective effects.

King’s College London researcher Amir Englund said: “In a previous study, about forty percent of volunteers experienced short-lived psychotic-like effects when given a high THC dose.

“Effects such as strange thoughts, suspicions or even hallucinations, and something we call conceptual disorganisation.

“When given big doses of CBD, people do not experience paranoia, less memory impairment and less likely to experience psychotic effects, so we want to find out, is there a CBD/THC ratio that’s less harmful?”

After inhaling different radios of CBD and THC at the start of the test volunteers listened to music and tasted chocolate to see if their appreciation of it changed through the day, as well as took a trip to the shop where they evaluated their social interaction experience.

Although the three year study has now finished the King’s team, who are working with King’s College Hospital and the South London and Maudsley NHS Trust are currently analysing the results.

For advice on the effects and risks of using cannabis visit


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