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Study: CBD May Increase THC Adverse Effects

Results from a new study have challenged beliefs held by some about the interaction of CBD and THC.

It’s been often claimed non-intoxicating cannabidiol (CBD) can reduce the intoxicating effects of tetrahydrocannabinol (THC), or some of the more undesirable effects.

But in a study led by Johns Hopkins Medicine researchers involving edibles (brownies), it was determined relatively high doses of CBD may increase the adverse effects of THC. The findings indicate CBD in the dosage used inhibited the metabolism of THC, which may result in actually stronger and longer drug effects.

However, it was also noted the fact THC and CBD were administered in edibles played a large role in the behavioral effects and drug interactions seen.

In a randomized clinical trial involving 18 adult participants, ingestion of 20 mg  THC + 640 mg CBD resulted in stronger subjective drug effects, greater cognitive and psychomotor impairment, and greater increase in heart rate compared to 20 mg THC alone and a placebo.

“These effects appear to be mediated by CBD inhibition of Δ9-THC and 11-OH-Δ9-THC metabolism,” states the study.

Among the subjective ratings and based on a scale of 0 – 100 in relation to effects:

  • overall drug effects: 59 [THC] vs. 73 [THC + CBD]
  • unpleasant drug effects: 20 [THC] vs. 39 [THC + CBD]
  • feeling sick: 12 [THC] vs. 26 [THC + CBD]
  • dry/red eyes: 16 [THC] vs. 29 [THC + CBD])
  • difficulty performing routine tasks: 30 [THC] vs. 47 [THC + CBD]

The researchers state that after eating the brownie with the high CBD cannabis extract, participants showed significantly more impairment in performance on tests of memory and attention compared with the brownie with only the high THC extract.

“Our new study suggests that it’s important for folks to be aware that if they’re going to take a high-dose CBD extract, they also need to be mindful about interactions with other medications,” said Ryan Vandrey, Ph.D., professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine; who is also the study’s senior author. “Individuals should discuss with their doctor whether they should consider dose adjustments of THC and other medications if they’re also taking CBD.”

The study has been published in JAMA Network Open and can be viewed here.

As Dr. Vandrey mentioned, caution regarding CBD doesn’t just apply to THC. A couple of years ago, Penn State College of Medicine researchers put together a list of dozens of medications that may not function as intended when used with cannabis products; including CBD oil.

Gillian Jalimnson
Gillian Jalimnson is one of Hemp Gazette's staff writers and has been with us since we kicked off in 2015. Gillian sees massive potential for cannabis in areas of health, energy, building and personal care products and is intrigued by the potential for cannabidiol (CBD) as an alternative to conventional treatments. You can contact Gillian here.

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