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CBD Amplifies the Adverse Effects of THC: New Study Finds



A new study has unearthed a controversy on the interaction between the psychoactive cannabinoid THC and its mellow counterpart CBD. For the longest time, it's been believed that combining CBD with THC enhances the therapeutic benefits of both while limiting some of the adverse effects attached to THC. The exact mechanisms have been hypothesized with the message being loud and clear; CBD is THC’s perfect complement and antidote. From this new study, it appears that this is not entirely the case. 

Details of the study

A group of researchers from John Hopkins University, Behavioral Pharmacology Research Unit conducted a randomized clinical trial to investigate the effects and side effects of cannabis edibles containing both THC and CBD in equal amounts.

The study model was a double blind crossover that included 18 healthy adults. This involved three randomized outpatient test sessions; each session one week apart. The participants were divided into three groups and offered brownies containing either of the three:

  • No cannabis extract (placebo)
  • 20 mg Δ9-THC with no CBD
  • 20 mg Δ9-THC + 640 mg CBD

The group that received CBD in addition to THC experienced more severe adverse effects compared to the THC only group. The researchers found that CBD inhibits the breakdown (metabolism) of THC. CBD thus increases the adverse effects of THC by increasing the circulating levels of THC and its active metabolite. The study was published in February 2023 in the JAMA Network Open Network and can be accessed here.  The study received funding from the National Institute on Drug Abuse (NIDA). 

Contradictory Evidence: Is There an Ideal Way to Mix CBD With THC

There are a number of studies whose results contradict the major claim in this article; CBD worsens the adverse effects of THC. Let’s look at a few of these:

A 2019 study was conducted by the Western University to investigate how CBD affects the psychiatric side effects of THC. The rats offered THC were more anxious and fearful while the rats that were offered both CBD and THC were less anxious and fearful.

The researchers found that CBD attenuates some of the psychotropic side effects caused by THC by inhibiting THC’s ability “to overstimulate the ERK pathway.” The results of the study were published in the Journal of Neuroscience.

A different systematic review investigated the influence of CBD on the acute effects of THC. The researchers found that in most studies CBD reduced the adverse effects of THC. 

However,  these studies have used different ratios of THC to CBD. With the medical cannabis industry taking shape, it's imperative to speed up research so as to find the best ways to offer cannabinoids to patients. 


Lydia K. (Bsc. RN) is a cannabis writer, which, considering where you’re reading this, makes perfect sense. Currently, she is a regular writer for Mace Media. In the past, she has written for MyBud, RX Leaf & Dine Magazine (Canada), CBDShopy (UK) and Cannavalate & Pharmadiol (Australia). She is best known for writing epic news articles and medical pieces. Occasionally, she deviates from news and science and creates humorous articles. And boy doesn't she love that! She equally enjoys ice cream, as should all right-thinking people.