Cannabis reliably increased psychotic-like symptoms but CBD did not blunt the effect
Two double-blind placebo-controlled studies found inhaled cannabis reliably increased psychotic-like symptoms and may increase speech illusions, but CBD in the cannabis did not reduce these effects, and adolescents were not more vulnerable than adults.
Quick Facts
What This Study Found
Cannabis increased psychotic-like symptoms (PSI scores) in both studies. In Study 2, cannabis increased the odds of speech illusion 3.1 times. Cannabis with CBD showed no difference from cannabis without CBD on psychotic outcomes (Study 1). Adults showed more psychotic-like symptoms than adolescents (Study 2), contrary to the hypothesis that adolescents would be more vulnerable.
Key Numbers
Study 1: 17 adults, no CBD protection; Study 2: 20 adolescents + 20 adults; speech illusion OR 3.1 (95% CI 1.3-7.2); adults showed more psychotic-like symptoms than adolescents
How They Did This
Two double-blind placebo-controlled studies. Study 1 compared cannabis with CBD vs without CBD in 17 adults. Study 2 compared cannabis effects in 20 adolescents vs 20 adults. All participants were healthy current cannabis users. Outcomes included Psychotomimetic States Inventory and speech illusion in a white noise task.
Why This Research Matters
The assumption that CBD protects against THC-induced psychotic effects has influenced cannabis product development and regulation. This study challenges that assumption in a controlled acute dosing paradigm.
The Bigger Picture
These findings challenge two popular assumptions: that CBD blunts THC's psychotic effects and that adolescents are acutely more vulnerable. However, acute effects may differ from chronic exposure patterns that contribute to long-term psychosis risk.
What This Study Doesn't Tell Us
Very small samples (17 and 40 participants). Single acute dose may not reflect chronic use patterns. Only healthy current cannabis users were tested, excluding the most vulnerable individuals.
Questions This Raises
- ?Would CBD protection emerge with repeated dosing rather than acute administration?
- ?Why were adults more susceptible to acute psychotic effects than adolescents?
- ?How do these acute findings relate to the epidemiological association between adolescent cannabis use and psychosis risk?
Trust & Context
- Key Stat:
- CBD did not blunt THC-induced psychotic-like symptoms
- Evidence Grade:
- Double-blind placebo-controlled design with rigorous methodology, but very small sample sizes limit statistical power.
- Study Age:
- Published in 2021.
- Original Title:
- Acute effects of cannabis on speech illusions and psychotic-like symptoms: two studies testing the moderating effects of cannabidiol and adolescence.
- Published In:
- Psychological medicine, 51(12), 2134-2142 (2021)
- Authors:
- Mokrysz, Claire(11), Shaban, Natacha D C(3), Freeman, Tom P(51), Lawn, Will, Pope, Rebecca A, Hindocha, Chandni, Freeman, Abigail, Wall, Matthew B, Bloomfield, Michael A P, Morgan, Celia J A, Nutt, David J, Curran, H Valerie
- Database ID:
- RTHC-03354
Evidence Hierarchy
Participants are randomly assigned to treatment or placebo groups to test cause and effect.
What do these levels mean? →Frequently Asked Questions
Does CBD protect against THC-induced psychotic effects?
Not in this study. Cannabis with CBD showed no difference from cannabis without CBD on psychotic-like symptoms or speech illusion in a controlled acute dosing study of 17 adults.
Are teenagers more vulnerable to psychotic effects of cannabis?
Surprisingly, no in this acute study. Adults actually showed more psychotic-like symptoms than adolescents. However, long-term risk from repeated adolescent use may still differ.
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Cite This Study
https://rethinkthc.com/research/RTHC-03354APA
Mokrysz, Claire; Shaban, Natacha D C; Freeman, Tom P; Lawn, Will; Pope, Rebecca A; Hindocha, Chandni; Freeman, Abigail; Wall, Matthew B; Bloomfield, Michael A P; Morgan, Celia J A; Nutt, David J; Curran, H Valerie. (2021). Acute effects of cannabis on speech illusions and psychotic-like symptoms: two studies testing the moderating effects of cannabidiol and adolescence.. Psychological medicine, 51(12), 2134-2142. https://doi.org/10.1017/S0033291720001038
MLA
Mokrysz, Claire, et al. "Acute effects of cannabis on speech illusions and psychotic-like symptoms: two studies testing the moderating effects of cannabidiol and adolescence.." Psychological medicine, 2021. https://doi.org/10.1017/S0033291720001038
RethinkTHC
RethinkTHC Research Database. "Acute effects of cannabis on speech illusions and psychotic-..." RTHC-03354. Retrieved from https://rethinkthc.com/research/mokrysz-2021-acute-effects-of-cannabis
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.