Low-dose CBD enhanced THC intoxication while high-dose CBD reduced it, especially in infrequent users
In a randomized controlled trial of vaporized cannabinoids, low-dose CBD (4 mg) enhanced THC intoxication while high-dose CBD (400 mg) reduced it, with infrequent cannabis users most affected by the enhancing effect.
Quick Facts
What This Study Found
CBD alone (400 mg) showed some intoxicating properties vs. placebo. When combined with 8 mg THC, low CBD (4 mg) enhanced intoxication while high CBD (400 mg) reduced it. The enhancement by low-dose CBD was especially prominent in infrequent cannabis users and consistent across objective and subjective measures. Most effects were significant at p < .0001.
Key Numbers
36 participants. 5 conditions. CBD alone (400 mg) was somewhat intoxicating. Low CBD (4 mg) + THC (8 mg) enhanced intoxication. High CBD (400 mg) + THC (8 mg) reduced intoxication. Effects significant at p < .0001.
How They Did This
Randomized, placebo-controlled trial with 36 participants (31 male) completing 5 drug conditions one week apart: placebo, CBD alone (400 mg), THC alone (8 mg), THC + low CBD (4 mg), THC + high CBD (400 mg). Administered by vaporization.
Why This Research Matters
This fundamentally challenges the simple narrative that "CBD counteracts THC." The dose matters enormously, and low-dose CBD (the ratio found in many commercial products) may actually make THC more intoxicating.
The Bigger Picture
Many cannabis products contain low CBD-to-THC ratios. This study suggests these products may be more intoxicating than THC alone, the opposite of what consumers expect. The vulnerability of infrequent users is particularly concerning.
What This Study Doesn't Tell Us
Relatively small sample (n=36). Predominantly male (31/36). Vaporization delivery may not generalize to other routes. Only two CBD doses tested, so the threshold for switching from enhancement to reduction is unknown.
Questions This Raises
- ?At what CBD dose does the effect switch from enhancement to reduction?
- ?Should product labels warn about low-dose CBD enhancement?
- ?Are commercial cannabis products inadvertently maximizing intoxication through low CBD content?
Trust & Context
- Key Stat:
- Low CBD enhanced intoxication; high CBD reduced it (p < .0001)
- Evidence Grade:
- Strong: randomized, placebo-controlled, within-subjects design with multiple conditions and objective/subjective measures.
- Study Age:
- Published in 2019.
- Original Title:
- A randomised controlled trial of vaporised Δ9-tetrahydrocannabinol and cannabidiol alone and in combination in frequent and infrequent cannabis users: acute intoxication effects.
- Published In:
- European archives of psychiatry and clinical neuroscience, 269(1), 17-35 (2019)
- Authors:
- Solowij, Nadia(19), Broyd, Samantha, Greenwood, Lisa-Marie(8), van Hell, Hendrika, Martelozzo, Dave, Rueb, Kuna, Todd, Juanita, Liu, Zheng, Galettis, Peter, Martin, Jennifer, Murray, Robin, Jones, Alison, Michie, Patricia T, Croft, Rodney
- Database ID:
- RTHC-02301
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 always reduce THC effects?
No. This study found that only high-dose CBD (400 mg) reduced THC intoxication. Low-dose CBD (4 mg) actually enhanced it. The commonly repeated claim that CBD counteracts THC is oversimplified.
Why were infrequent users more affected?
Infrequent users may have less tolerance and more sensitive cannabinoid systems, making them more susceptible to the enhancing effect of low-dose CBD on THC intoxication.
Read More on RethinkTHC
- THC-purity-potency-label-meaning
- dab-concentrate-addiction-withdrawal
- delta-8-addiction-withdrawal
- edible-addiction-withdrawal-different
- edibles-psychosis-emergency-room
- healthiest-way-to-consume-cannabis
- how-cannabis-products-made-concentrates-edibles
- laced-weed-fentanyl-contaminated-vape
- legal-weed-vs-street-weed-quality-safety
- quitting-dabs-withdrawal
- quitting-edibles-withdrawal
- sativa-vs-indica-difference-myth
- weed-potency-withdrawal
Cite This Study
https://rethinkthc.com/research/RTHC-02301APA
Solowij, Nadia; Broyd, Samantha; Greenwood, Lisa-Marie; van Hell, Hendrika; Martelozzo, Dave; Rueb, Kuna; Todd, Juanita; Liu, Zheng; Galettis, Peter; Martin, Jennifer; Murray, Robin; Jones, Alison; Michie, Patricia T; Croft, Rodney. (2019). A randomised controlled trial of vaporised Δ9-tetrahydrocannabinol and cannabidiol alone and in combination in frequent and infrequent cannabis users: acute intoxication effects.. European archives of psychiatry and clinical neuroscience, 269(1), 17-35. https://doi.org/10.1007/s00406-019-00978-2
MLA
Solowij, Nadia, et al. "A randomised controlled trial of vaporised Δ9-tetrahydrocannabinol and cannabidiol alone and in combination in frequent and infrequent cannabis users: acute intoxication effects.." European archives of psychiatry and clinical neuroscience, 2019. https://doi.org/10.1007/s00406-019-00978-2
RethinkTHC
RethinkTHC Research Database. "A randomised controlled trial of vaporised Δ9-tetrahydrocann..." RTHC-02301. Retrieved from https://rethinkthc.com/research/solowij-2019-a-randomised-controlled-trial
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.