In a rigorous multi-site trial, oral CBD at doses up to 800 mg did not reduce the subjective high, reinforcing effects, or cardiovascular impact of smoked cannabis in regular users.
Read this if you believe CBD products can reduce the effects of THC or help moderate cannabis use.
CBD up to 800 mg failed to reduce any measured effect of smoked cannabis
What the researchers found
Some studies have suggested that CBD can counteract certain effects of THC, leading to widespread claims that CBD-rich products might reduce the downsides of cannabis use. This randomized, double-blind study tested that idea rigorously.
Thirty-one healthy cannabis smokers completed eight sessions where they received oral CBD (0, 200, 400, or 800 mg) 90 minutes before smoking either active or inactive cannabis. CBD alone produced no significant psychoactive or cardiovascular effects.
The key finding: CBD at any dose did not reduce the high, the positive subjective effects, the self-administration of cannabis, or the heart rate increase caused by smoked cannabis. Participants were just as likely to choose active cannabis over placebo cannabis regardless of CBD pretreatment.
Why it matters
This study directly challenges the popular notion that CBD counteracts THC. The failure of even very high CBD doses (800 mg) to blunt any measured effect of smoked cannabis suggests that adding CBD to cannabis products may not meaningfully reduce intoxication or the desire to use more.
The numbers in context
31 participants (17 male, 14 female). CBD doses: 0, 200, 400, 800 mg oral. Cannabis: 5.30-5.80% THC. Eight sessions per participant. No significant effect of CBD on any outcome at any dose.
How the study worked
Multi-site, randomized, double-blind, within-subject laboratory study. Thirty-one non-treatment-seeking cannabis smokers completed eight outpatient sessions testing four CBD doses against two cannabis conditions. A subset of 8 participants had plasma CBD levels measured after the 800 mg dose.
What this study cannot tell us
The cannabis used (5.3-5.8% THC) was lower potency than much of what is available today. CBD was given orally while cannabis was smoked, creating different pharmacokinetic profiles. Participants were regular users who may have different responses than occasional users.
How to read the evidence
Multi-site randomized double-blind within-subject design with multiple CBD doses. Strong methodology, though moderate sample size.
When this study was published
Published in 2016. The cannabis tested was lower potency than many current products, and CBD formulations have evolved.
The bigger picture
The CBD market is built partly on the idea that CBD moderates THC effects. This well-designed human study found no evidence for that claim across multiple outcomes including the high, liking, strength ratings, and self-administration. Previous positive findings may have been artifacts of studying single doses of oral THC rather than real-world smoked cannabis.
Questions still open
- Would inhaled CBD produce different results than oral CBD? Does the CBD-THC interaction depend on the route of administration or timing? Are previous claims about CBD counteracting THC based on artifacts of study design?
Common questions
Does CBD counteract the effects of THC?
Why is this different from what I have heard about CBD?
Read the original research
Oral Cannabidiol does not Alter the Subjective, Reinforcing or Cardiovascular Effects of Smoked Cannabis.
Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 41(8), 1974-82
Citation
Haney, Margaret; Malcolm, Robert J; Babalonis, Shanna; Nuzzo, Paul A; Cooper, Ziva D; Bedi, Gillinder; Gray, Kevin M; McRae-Clark, Aimee; Lofwall, Michelle R; Sparenborg, Steven; Walsh, Sharon L. (2016). Oral Cannabidiol does not Alter the Subjective, Reinforcing or Cardiovascular Effects of Smoked Cannabis.. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 41(8), 1974-82. https://doi.org/10.1038/npp.2015.367
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