Written By Chantelle Pattemore | Edited By Gillian Mohney | Fact Checked By Jennifer Chesak

Milles Studio/Stocksy

Many studies have explored the effects of cannabis and its two main components — cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC) — on the body.

Some previous research has suggested that CBD can dampen some of THC’s less desirable effects, such as anxiety and memory impairment.

However, a new study conducted by a team at University College London (UCL) has indicated this might not be the case.

What the study found

The study published February 7 involved 48 regular cannabis users: 24 adolescents (aged 16-17) and 24 adults (aged 26-29).

Under close medical supervision on separate occasions, they were each given three forms of vaporized cannabis — a placebo, a strain high in THC, and a strain high in THC and CBD (at a ratio of 1:3).

It was found that, between the high THC and high THC and CBD forms, there was no variation in the subjective ‘feel’ caused by the drug. There were also no differences in psychoactive effects and memory impairment.

This is particularly interesting because the researchers saw that, when paired with CBD, levels of THC in the blood were higher. Yet, despite this, “there were no behavioral effects,” stated Dr. Will Lawn, Psychology Lecturer at King’s College London and Lead Author of the study.

Lawn noted that these “quite complicated pharmacokinetic results…are surprising” and that he and his team are “unsure” as to why they might have occurred.

So why is it thought that CBD might aid in decreasing some of THC’s effects?

“The possibility that CBD might counter the intoxicating effects of THC was suggested many years ago,” said Daniele Piomelli, PhD, Director of the UCI Center for the Study of Cannabis in Irvine, CA.

It arose “as a possible explanation for the different effects of cannabis preparations that contain different ratios of the two chemicals,” he told Healthline.

However, in general, the potential counter-effect “is not clearly understood,” explained Dr. David Berger, a pediatrician based in Florida and medical director of the medical cannabis clinic Wholistic ReLeaf.

He shared with Healthline that “there is discussion that it is related to altering an enzyme called extracellular-signal-regulated kinase (ERK) in the hippocampus of the brain. It is felt this enzyme is connected to the euphoric effects of THC.”

Furthermore, Berger noted, “there is also discussion that CBD may alter the amount of calcium inside the neurons.

In addition to exploring whether CBD mitigated some of THC’s effects, the researchers also looked at the immediate harmful impacts of cannabis on the two age groups.

They hypothesized that adolescents would be more vulnerable and feel the effects more acutely.

However, this was not the case: they saw no difference in outcomes between the adult and teen participants.

“Teenagers may not be more vulnerable to associations with cognitive impairment and depression and anxiety,” Lawn stated to Healthline. “[There are] very mixed results throughout the literature.”

However, that doesn’t mean it’s a good idea for adolescents to start using cannabis.

Furthermore, adolescence is a critical time of development — and THC use can have long-term effects on this.

“It is felt that brains are still developing until about 25 years old,” stated Berger.

“Any significant use of THC prior to this age will probably have a bigger impact on the long-term health of the brain than starting when older,” he said.

Yet it’s thought that THC affects more than just brain development in adolescence — and “understanding what functions might be affected by cannabis use in adolescence is an area of active research,” shared Piomelli.

“The receptors are normally activated by our own ‘cannabis’, the so-called endocannabinoids, which are produced in tiny amounts when and where they are needed,” he told Healthline.

“THC in cannabis can mess up this delicate balance of signals. This is especially problematic in adolescence, when endocannabinoids are thought to contribute to important aspects of development.”

What are CBD and THC?

CBD and THC are both cannabinoids, but they influence the body and brain in different ways.

“They have different molecular structures, therefore bind at the receptor sites differently,” Dr. Brooke Worster, FACP, Chief Medical Advisor at Ethos Cannabis, explained to Healthline.

Piomelli revealed that “THC activates cannabinoid receptors, cellular proteins found throughout the body that help control important processes such as mood, stress-coping, and pain.”

As such, it “is responsible for the intoxicating effects of cannabis.”

On the flip side, he noted, “CBD does not activate cannabinoid receptors, and its mechanism of action is still debated.”

So how do they interact with the body?

“All cannabinoids ‘work’ through binding and activating or blocking of the receptors in the endocannabinoid system,” shared Worster. “This, in turn, has complicated effects on all kinds of brain functions.”

She continued that the associations still need to be better understood. “There is much unknown about how the endocannabinoid system interacts with these other receptors in our brains.”

The effects of CBD and THC

According to Worster, the “short-term effects of THC are related to cognitive processing, reaction time, short-term memory — akin to alcohol intoxication.”

Additionally, Berger noted, “some patients who take THC can experience panic or paranoia.”

Meanwhile, Worster said, the “long-term effects are related to motivation and cognitive processing, as well as the possible development of cannabis use disorder.”

With regards to CBD, Worster continued, the “short- and long-term effects are less known, but are believed to impact the immune response in the body.”

When using cannabis in general, “the most concerning side effect is impact on memory and cognitive function,” stated Berger.

“While some research shows that smoking alters the lungs in the long term, other studies do not,” he continued. “As a rule, I do not recommend people smoke anything.”


New UK study findings suggest that CBD does not cancel out some of the adverse effects arising from THC in cannabis. These results contrast with previous scientific findings.

For instance, “evidence from animal studies supports this idea [that CBD can negate THC’s impacts],” shared Piomelli. As such, “we should not be too quick to rule it out.”

Berger agreed that it’s essential to look at the bigger picture when considering these findings.

“Some studies support this paper’s findings that CBD does not protect against THC negative effects. However, other papers suggest CBD does offer protection against THC,” he revealed. “Many studies should be reviewed before drawing strong conclusions.”

In light of this, Berger continued, “this new paper should not be considered definitive evidence, but rather part of a growing body of data that addresses the hypothesis that CBD is protective against some of the negative effects of THC.”

While the researchers also noted that the immediate effects of vaporized cannabis on adolescents did not vary compared to adults, concerns remain around the longer-term impacts of the drug on their development.

“Obviously, it’s still wise not to encourage teenage cannabis use!” stated Lawn.



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