Study: High-CBD Edibles Result in Stronger Effects

CBD edibles on pink background
A recent study published in the Journal of the American Medical Association challenges the common belief that cannabidiol (CBD) mitigates the psychoactive effects of tetrahydrocannabinol (THC) in cannabis. The research found that edibles with high CBD content can actually enhance the psychoactive effects of THC, leading to a stronger and less enjoyable high. This effect was particularly noticeable in infrequent cannabis users. The study suggests that this could be due to the ways in which CBD slows the metabolism of THC when cannabis is consumed in edible form.
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“THC gets you high. CBD mellows the high.” – The problem with this simplistic explanation of marijuana’s two primary cannabinoids is that it’s not always true. Especially when it comes to edible cannabis.

According to a new study released in the Journal of the American Medical Association:

Cannabis edibles with an elevated CBD content can actually increase the psychoactive effects of THC, creating a stronger and less enjoyable high. This revelation runs counter to popular assumptions on THC:CBD ratios, and contradicts the idea that CBD “takes the edge off.”

Digging a bit deeper into the subject yields some understanding regarding current assumptions on CBD and possible explanations for this newly discovered phenomenon.

THC & CBD: A Complex Relationship

CBD was first identified as a unique cannabinoid more than 80 years ago. But because it lacks the intoxicating properties of THC, little research was devoted to its pharmacodynamic effects in the following decades. Instead, most research focused on THC. An example of this trend comes from a 1975 study which determined that increased dosages of CBD did delay the onset and prolong the effects of THC, but only by a small amount.

As a result, the authors concluded:

[There] is no need to abandon the current practice of basing doses of marijuana for clinical studies solely on THC content.

By the late 1980s, the discovery of the human endocannabinoid system resulted in renewed interest in the relationship between CBD and THC. Research revealed that CBD does not bind with the human body’s CB1 and CB2 cannabinoid receptors in the same way as THC, but it can regulate and reduce the uptake of THC by these receptors.

CBD earned additional respect as it was shown to play a therapeutic role in mitigating rheumatic inflammation, oxidative stress, anxiety, convulsive disorders, and symptoms of psychosis associated with schizophrenia. These benefits now serve as the basis for CBD’s widely-touted reputation as “the healing herb.”

When cannabis research pioneer Raphael Mechoulam suggested that cannabinoids taken together in whole-plant form created a synergistic entourage effect, it helped solidify the idea of CBD and THC as marijuana’s “perfect pair.” This set the stage for a new wave of research devoted to the effects of various THC:CBD formulations.

Typical of this research was a study published in the British Journal of Psychology involving subjects evaluated for memory recall after smoking marijuana with a low CBD content, then retested after smoking marijuana with the same THC content and a much higher CBD content.

Results showed that:

Unlike the marked impairment in prose recall of individuals who smoked cannabis low in cannabidiol, participants smoking cannabis high in cannabidiol showed no memory impairment. Cannabidiol content did not affect psychotomimetic symptoms, which were elevated in both groups when intoxicated.

The authors went on to add:

Users should be made aware of the higher risk of memory impairment associated with smoking low-cannabidiol strains of cannabis like “skunk” and encouraged to use strains containing higher levels of cannabidiol.

In a 2019 study, subjects were given a range of vaporized THC:CBD formulas and evaluated for intoxicating effects by both objective and subjective measures. The authors concluded that:

  • Low doses of CBD when combined with THC enhanced intoxicating effects.
  • High doses of CBD reduced the intoxicating effects of THC.
  • The enhancement of intoxication by low-dose CBD was particularly prominent in infrequent cannabis users.

Statements such as this have led to the popular assumption that increasing the CBD content in a cannabis product reduces the negative effects of THC, while maintaining benefits such as pain reduction, anxiety relief, and neuroprotection. However, a majority of researchers caution that such assumptions should not be taken as gospel, as there are still many variables and unknowns surrounding the pharmacodynamics of cannabis consumption.

In addition, it should be noted that most all studies to date on THC:CBD ratios were conducted using smoked or vaporized cannabis rather than edibles.

New Edibles Study Challenges CBD Assumptions

The findings that made recent headlines and inspired this post come from a research team at the Johns Hopkins University School of Medicine and several branches of the University of Washington. In a first-of-its-kind study, 18 volunteers who were identified as infrequent cannabis users consumed a marijuana-laced brownie containing 20mg THC and were then evaluated for subjective drug effects, objective cognitive, psychomotor performance, and a range of vital signs. After an interval of at least one week, subjects were then given a brownie with an equivalent 20mg dose of THC, this time combined with 640mg CBD. Results were also measured after participants consumed a placebo brownie with no THC or CBD content.

Study leader Dr. Austin Zamarrip describes the results as “pretty remarkable.” Instead of mitigating the intoxicating effects of THC, the brownies containing a high dose of CBD had the opposite effect. Testing revealed that as compared to the THC-only brownies, those with added CBD created negative effects, such as:

  • Significantly greater impairments to cognition and hand-eye coordination exercises
  • Higher peak THC blood plasma levels
  • More significant impairments to memory and attention
  • An increase in heart rate
  • Longer duration of impairments

Subjects were also asked to describe the effects of the brownies, including their perceived degree of impairment, positive experiences while high, and negative sensations such as anxiety, paranoia, nausea, and dry mouth. In all cases, users reported more negative effects from the CBD-laced brownies than from THC-only brownies.

While the study didn’t speculate on the possible reasons for the negative effects of the high CBD brownies, Dr. Zamarrip did note that it may be related to the ways in which CBD slows the metabolism of THC when cannabis is consumed in edible form.

Know Your CBD: THC Formulas

In a discussion of results, the authors stressed the need for consumer education and the importance of future research on edible cannabis formulations. They write:

Research is particularly needed to understand the association of CBD with delta-9-THC, because there is a high degree of variability in CBD content across cannabis products, and products are marketed and used based on the content and ratios of delta-9-THC:CBD.

And there is an added variable in the equation. Research has identified significant variations in the dose and label accuracy of edible cannabis products. A research letter published in the Journal of the American Medical Association reported that of 75 products purchased from 45 separate dispensaries in California and Washington:

  • 17% were accurately labeled with respect to THC content
  • 23% were under-labeled
  • 60% were over-labeled

Medical marijuana patients who are choosing edible cannabis for therapies should keep these factors in mind when choosing a product and a provider. All products should be sourced from a reputable, state-licensed dispensary that provides accurate labeling. Patients should also consult with medical professionals who are trained and experienced in cannabis-based therapies, including edible formulas.

Updated: May 28, 2024

Article Written By: ,

Pierce Hoover

Pierce Hoover is a career journalist with more than three decades of experience in print, broadcast and online writing, editing and reporting, with more than 5,000 articles published in national and international print media and online. His focus on medical marijuana therapies mirrors his broader interest in science-based alternative medical practices.


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