Department of Pharmacology

Linda Klumpers, Ph.D., M.Sc., research assistant professor of pharmacology

(APRIL 5, 2024) Linda Klumpers, Ph.D., M.Sc., research assistant professor of pharmacology, commented in an SFGATE article about the first clinical evidence that terpenes can change the effects of THC.

Researchers at Johns Hopkins University recently published results from a clinical trial showing that adding a specific terpene—limonene, chosen because there was already significant pre-clinical research showing that it has psychoactive effects and because the cannabis industry is already making claims based on the compound—to THC in cannabis products changed the experience of getting high. This is the first clinical evidence that terpenes can change the effects of THC.

The researchers said the study’s findings could be used to make medical cannabis products more useful by reducing the amount of anxiety caused by THC, one of the negative side effects of using the drug.

Klumpers, along with another research scientist and a medical doctor (all unaffiliated with the study), told SFGATE this latest research is groundbreaking, as it’s the first published clinical trial to test the effects of a terpene in combination with THC. She called the study “successful” and said it shows the combination of THC and limonene “likely gives effects that are different from when the compounds are given alone.”

Klumpers did, however, caution that the study has several limitations and doesn’t prove that terpenes found in natural pot products affect how people experience THC intoxication. The study’s sample size was small—only 12 people—and the inclusion of many different measurements reduced the overall strength of its conclusions, according to Klumpers. The study also did not blind the aroma of limonene, meaning participants could have been aware they were consuming a terpene along with the THC. In addition, the group that reported the strongest effects received doses of limonene higher than anything naturally found in cannabis, limiting its real-world relevance.

Despite these caveats, the Hopkins team has filed a patent application for combining limonene and THC to reduce THC-induced anxiety, suggesting the team believes there are possible pharmaceutical uses for its findings.