A Clinical Trial Testing Whether a High-CBD Cannabis Oil Affects Thinking and Mood
A single dose of a 20:1 CBD:THC medicinal cannabis oil mildly impaired some memory functions while slightly improving mood in healthy adults.
Quick Facts
What This Study Found
A sublingual dose of CannEpil (100mg CBD, 5mg THC) impaired visuospatial working memory and delayed pattern recognition compared to placebo, but largely preserved mood. Participants felt more content and amicable about 2.5 hours after dosing. About 23% reported drowsiness between 3 and 6 hours post-dose.
Key Numbers
31 participants. 100mg CBD + 5mg THC sublingual dose. Contentedness (p<0.01) and amicability (p<0.05) improved at 2.5 hours. 23% reported drowsiness 3-6 hours post-dose.
How They Did This
Randomized, double-blind, placebo-controlled, within-subjects crossover trial with 31 healthy participants (16 female, 15 male) aged 21-58 over a two-week protocol.
Why This Research Matters
As CBD-dominant products gain medical acceptance, knowing their acute cognitive effects is essential for safety, especially for users who drive or work.
The Bigger Picture
The mild cognitive effects alongside mood improvement reflects the tradeoff many medicinal cannabis users face. The lack of correlation between plasma levels and cognitive changes suggests individual differences may matter more than dose.
What This Study Doesn't Tell Us
Small sample (n=31) of healthy volunteers may not reflect patients with medical conditions. Single-dose design does not capture effects of repeated use. Only one CBD:THC ratio was tested.
Questions This Raises
- ?Would tolerance develop to the cognitive effects with repeated dosing?
- ?Do patients with existing cognitive impairment experience greater effects than healthy volunteers?
Trust & Context
- Key Stat:
- 100mg CBD + 5mg THC mildly impaired memory but improved mood; 23% reported drowsiness
- Evidence Grade:
- Rigorous RCT design with double-blinding and crossover, but small sample size limits power.
- Study Age:
- Published in 2024.
- Original Title:
- A randomised, placebo-controlled, double blind, crossover trial on the effect of a 20:1 cannabidiol: Δ9-tetrahydrocannabinol medical cannabis product on neurocognition, attention, and mood.
- Published In:
- European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology, 82, 35-43 (2024)
- Authors:
- Manning, Brooke(6), Hayley, Amie C(8), Catchlove, Sarah(3), Stough, Con, Downey, Luke A
- Database ID:
- RTHC-05509
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 high-CBD cannabis oil affect your thinking?
This trial found mild impairments in spatial working memory and pattern recognition after a single dose of 100mg CBD/5mg THC, though most cognitive functions were preserved.
Does CBD make you drowsy?
About 23% of participants reported drowsiness 3-6 hours after taking the CBD-dominant product, with notable variability between individuals.
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Cite This Study
https://rethinkthc.com/research/RTHC-05509APA
Manning, Brooke; Hayley, Amie C; Catchlove, Sarah; Stough, Con; Downey, Luke A. (2024). A randomised, placebo-controlled, double blind, crossover trial on the effect of a 20:1 cannabidiol: Δ9-tetrahydrocannabinol medical cannabis product on neurocognition, attention, and mood.. European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology, 82, 35-43. https://doi.org/10.1016/j.euroneuro.2024.02.002
MLA
Manning, Brooke, et al. "A randomised, placebo-controlled, double blind, crossover trial on the effect of a 20:1 cannabidiol: Δ9-tetrahydrocannabinol medical cannabis product on neurocognition, attention, and mood.." European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology, 2024. https://doi.org/10.1016/j.euroneuro.2024.02.002
RethinkTHC
RethinkTHC Research Database. "A randomised, placebo-controlled, double blind, crossover tr..." RTHC-05509. Retrieved from https://rethinkthc.com/research/manning-2024-a-randomised-placebocontrolled-double
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.