Adding CBD to THC Doesn’t Reduce the Effects of Cannabis, Study Shows

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Some research indicates that CBD can mitigate the effects associated with cannabis products containing THC, but a recent study suggests otherwise. Juanma Hache/Getty Images
  • Some research has suggested that CBD can mitigate the effects associated with cannabis products containing THC.
  • A recent study has found the inverse, suggesting that inhaling CBD alongside THC did not protect participants from the short-term effects of a THC “high.”
  • Some experts say that consuming CBD alongside or after THC could reduce the psychoactive effects of cannabis for some people.
  • Larger studies are still needed to determine whether adding CBD to THC changes the pleasurable or unpleasant effects of cannabis.

The cannabis plant contains hundreds of different compounds. This includes tetrahydrocannabinol (THC), the main intoxicating compound, as well as cannabidiol (CBD), which doesn’t induce the same kind of “high.”

As seen with THC and CBD, both of which contain a type of compound called cannabinoids, cannabis compounds may have very different effects.

So when people use cannabis products, what they experience depends on which compounds are present and in what amounts.

Some research has suggested that CBD can reduce some of the effects associated with delta-9-THC, such as changes in memory and attention, as well as delusions, hallucinations, and similar effects.

However, other research has found no impact of CBD on delta-9-THC effects.

In a new study, researchers from the United Kingdom and Australia tested different CBD-to-THC ratios to clarify how CBD and THC work in the body when inhaled together.

The results, published on Nov. 16 in the journal Neuropsychopharmacology, show no evidence that CBD reduces the negative or pleasurable effects of THC.

In the study, researchers recruited 46 healthy volunteers ages 21 to 50 years old who had used cannabis in the past but not more than once per week during the previous year.

Over the course of four experiments, participants inhaled cannabis vapor containing 10 milligrams (mg) of THC combined with a different level of CBD (0 mg, 10 mg, 20 mg, or 30 mg).

Study author Amir Englund, PhD, a research fellow at King’s College London’s Institute of Psychiatry, Psychology & Neuroscience, told Healthline they chose these CBD-to-THC ratios because they’re representative of the majority of cannabis products consumed for recreational purposes.

After using cannabis, participants completed a series of tasks to measure the short-term impact of THC and CBD on their cognitive performance and how pleasurable the experience was.

Researchers also measured symptoms such as delusions, conceptual disorganization, hallucinations, hyperactivity, grandiosity, suspiciousness, and hostility — what they classified as “psychotic symptoms.”

Results showed that inhalation of CBD alongside THC did not protect participants from the short-term effects of THC.

In addition, researchers found that THC increased the pleasure experienced by participants while listening to a favorite song and tasting a piece of chocolate. Different levels of CBD did not reduce this.

The only difference that researchers observed was that participants coughed more as the CBD level increased.

Englund said the main limitation of their study is they didn’t have a placebo condition, in which people inhale vapor without THC or CBD. This would have allowed the researchers to compare the effects of inhaling vapor only to THC by itself. This limitation, of course, may bias the results.

“Like much psychedelic research, placebo comparisons become difficult because the vast majority [of people] will be relatively certain if they’ve had the drug or not since the intoxication is quite pronounced,” he said.

In future studies, Englund and his colleagues would like to try to determine the THC dose at which people start to experience effects such as anxiety, paranoia, and memory problems.

“This will give users practical information about how to avoid unwanted effects,” he said.

Daniele Piomelli, PhD, director of the UCI Center for the Study of Cannabis in Irvine, CA, told Healthline the study was well done — but he disagrees with the researchers’ classification of certain effects of THC as “psychotic symptoms.”

“There is no evidence that if you and I were to smoke pot that we would be psychotic,” he said. “We would be high. We would be stoned. But we would not be psychotic.”

However, Piomelli pointed out there’s some evidence to suggest that cannabis use among adolescents, particularly in high doses, is associated with a greater incidence of psychotic episodes later on in life. But this differs from the short-term effects experienced by most cannabis users.

Instead of using a term such as “psychosis,” Piomelli said he prefers to describe the effects of cannabis in more neutral terms — although he admits that not all cannabis researchers agree with him.

“Cannabis has certain effects — some people may like them, some people may not,” Piomelli said.

“As long as you’re not harming other people or making your own life problematic, I don’t think we should say that you’re experiencing psychosis.”

With this in mind, PIomelli noted the study’s key finding that adding CBD on top of THC will not change the high associated with THC.

“This is useful to know when dealing with a complex mixture of different compounds,”

Autumn Shelton, partner and chief financial officer of Autumn Brands, a cannabis business located in Carpinteria, CA, explained that because cannabis is made up of over a hundred cannabinoids and other compounds, it’s difficult to make broad claims about its effects — especially based on a study with a small number of participants.

“Cannabis is a complex plant,” she told Healthline. “Every person reacts differently to different levels of cannabis, as well as to how it’s consumed.”

For example, Shelton said the effects will differ for inhaled cannabis versus edibles and whether the product contains the whole plant or is distilled.

In her experience, though, she has found that consuming CBD alongside or after THC reduces the psychoactive effects.

“It all depends on the person,” she said. “These effects could be minimal to substantial. Different strains, types of cannabis, terpenes, esters, etc., also come into play.”

Englund said that people may have fewer negative effects with higher-CBD cannabis plant varieties because they tend to have lower THC levels.

“Because cannabis produces both THC and CBD from the same precursor in the plant, a cannabis variety with a greater amount of CBD will be naturally lower in THC,” he said.

“This makes it more difficult to over-consume and experience unwanted effects [of THC], compared to [using] THC dominant varieties.”

Shelton added that because of the wide range of effects that people can experience, consumers who are new to cannabis should start with a low dose and try different strains to find out what works best for them.

“If you decide to inhale [cannabis] flower, start with just a couple hits off a joint,” she said. “Or if you want to try an edible, start with 2.5 mg of THC or a 1:1 CBD-to-THC ratio.”

New research shows that adding CBD to THC will not alter the effects of a THC “high,” despite other studies that have suggested otherwise.

Be that as it may, the effects of using CBD and THC together may vary from person to person.

Those who use cannabis but wish to minimize the side effects — negative or pleasurable — might try reducing their intake or swapping THC for CBD altogether.