Acute effects of cannabis on speech illusions and psychotic-like symptoms: two studies testing the moderating effects of cannabidiol and adolescence

Claire Mokrysz, Natacha D C Shaban, Tom P Freeman, Will Lawn, Rebecca A Pope, Chandni Hindocha, Abigail Freeman, Matthew B Wall, Michael A P Bloomfield, Celia J A Morgan, David J Nutt, H Valerie Curran

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BACKGROUND: Acute cannabis administration can produce transient psychotic-like effects in healthy individuals. However, the mechanisms through which this occurs and which factors predict vulnerability remain unclear. We investigate whether cannabis inhalation leads to psychotic-like symptoms and speech illusion; and whether cannabidiol (CBD) blunts such effects (study 1) and adolescence heightens such effects (study 2).

METHODS: Two double-blind placebo-controlled studies, assessing speech illusion in a white noise task, and psychotic-like symptoms on the Psychotomimetic States Inventory (PSI). Study 1 compared effects of Cann-CBD (cannabis containing Δ-9-tetrahydrocannabinol (THC) and negligible levels of CBD) with Cann+CBD (cannabis containing THC and CBD) in 17 adults. Study 2 compared effects of Cann-CBD in 20 adolescents and 20 adults. All participants were healthy individuals who currently used cannabis.

RESULTS: In study 1, relative to placebo, both Cann-CBD and Cann+CBD increased PSI scores but not speech illusion. No differences between Cann-CBD and Cann+CBD emerged. In study 2, relative to placebo, Cann-CBD increased PSI scores and incidence of speech illusion, with the odds of experiencing speech illusion 3.1 (95% CIs 1.3-7.2) times higher after Cann-CBD. No age group differences were found for speech illusion, but adults showed heightened effects on the PSI.

CONCLUSIONS: Inhalation of cannabis reliably increases psychotic-like symptoms in healthy cannabis users and may increase the incidence of speech illusion. CBD did not influence psychotic-like effects of cannabis. Adolescents may be less vulnerable to acute psychotic-like effects of cannabis than adults.

Original languageEnglish
Pages (from-to)2134 - 2142
Number of pages9
JournalPsychological Medicine
Issue number12
Early online date28 Apr 2020
Publication statusPublished - 30 Sept 2021

Bibliographical note

Funding Information:
Acknowledgements. Study 1 was funded by Drug Science, Channel 4

Publisher Copyright:
Copyright © The Author(s), 2020. Published by Cambridge University Press.


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