CBD Could Worsen Effects of THC in Brownies, Other Products

FRIDAY, Feb. 17, 2023 (HealthDay News) -- There's a popular notion that cannabidiol (CBD) can take the edge off the less pleasant effects of marijuana. But a new study suggests that, when it comes to edibles, the opposite is true.

Researchers found that when they gave study volunteers a batch of pot brownies, the effects were as one would expect.

The surprise came when they tested brownies laced with both THC (the active ingredient in marijuana) and CBD, a non-intoxicating extract of the marijuana plant: The combo brownies were substantially more impairing than those containing THC alone.

Overall, they revved up people's heart rates to a greater degree, and caused bigger impairments in tests of memory and attention. And it was not in service of a "better" high: People also reported feeling lousier after eating the THC/CBD brownie — contrary to the belief that CBD counters the unwanted side effects of marijuana, like anxiety and sedation.

"It was a pretty remarkable effect," said study leader Austin Zamarripa, a postdoctoral researcher at Johns Hopkins University School of Medicine, in Baltimore.

Based on the researchers' analysis, it appears that CBD slows down the metabolism of THC — at least when it's taken in the form of an edible. And that intensifies and prolongs the effects of the drug, Zamarripa said.

CBD is one of hundreds of chemicals found in cannabis plants, including marijuana and hemp. It is more abundant in hemp — which, unlike marijuana, has little THC.

In 2018, Congress lifted a decades-old ban on growing hemp, and soon after there was an explosion of CBD products on the market. The chemical was being added to everything from oils and lotions to gummies and cookies, with claims that it could ease a host of ailments, including chronic pain, anxiety and insomnia.

Yet there is little scientific proof to back up those claims. And, Zamarripa said, there is a lot to learn about how CBD might interact with medications.

"CBD became widely available and spread much faster than (researchers) could study it," Zamarripa said.

At the same time, marijuana legalization has triggered a surge in use of marijuana edibles. So the Hopkins team wanted to see how CBD and oral THC, specifically, might interact.

They recruited 18 healthy young adults to do a brownie study. Each participant ate one brownie with a 20-milligram dose of THC, another with the same amount of THC plus 640 mg of CBD, and one cannabis-free brownie (the placebo). They consumed the treats at the research lab on three separate occasions, one week apart.

Overall, the researchers found, the combo brownie caused a substantially greater spike in people's blood levels of THC and heart rate, compared to the THC-only treat.

Meanwhile, participants' performance on tests of attention, in-the-moment "working" memory, and psychomotor skills — like the abilities people need for driving — deteriorated to a greater degree after the CBD/THC brownie.

The CBD dose used in the brownie was high, Zamarripa said. But, he added, it's also within the range of what a person might take in a day if they were trying to manage pain or anxiety, for example.

"Studies like this highlight that you need to be cautious when using these products, especially if you're also taking medications," Zamarripa said.

People might assume that because CBD is everywhere and marketed for an array of health benefits, it has been proven safe and effective. They would be wrong.

"The number and variety of health claims for CBD should vastly increase consumers' level of skepticism," said Dr. Peter Lurie, president of the nonprofit Center for Science in the Public Interest.

Lurie, who was not involved in the new research, called it "well done."

"I think this emphasizes the importance of having some kind of regulatory pathway for CBD," he said.

Right now, CBD oversight is in a state of limbo. Last month, the U.S. Food and Drug Administration said it cannot regulate CBD as a dietary supplement, due to a lack of evidence on its safety. The agency also called on Congress to create new rules on how to regulate the products.

Lurie said that as it stands, there is no way for consumers to know how much CBD is in a given product, or whether it is contaminated with THC.

"One of the problems with an unregulated market is that quality control is poor," Lurie said.

He, too, urged people to be cautious about CBD products, particularly if they are taking medications.

Unfortunately, there is not much specific advice to be given in that regard. At this point, Zamarripa said, it would be difficult for people to find good information on whether CBD interacts with their particular medications.

The findings were published online Feb. 13 in JAMA Network Open.

More information

The U.S. Food and Drug Administration has more on CBD.

SOURCES: Austin Zamarripa, PhD, postdoctoral research fellow, Johns Hopkins University School of Medicine, Baltimore; Peter Lurie, MD, MPH, president/executive director, Center for Science in the Public Interest, Washington, D.C.; JAMA Network Open, Feb. 13, 2023, online