A Johns Hopkins Medicine-led research team has added to evidence that a chemical found naturally in cannabis (also known as marijuana) can—in the right amounts—lessen the anxiety-inducing effects of THC, the primary psychoactive component in cannabis. This finding has the potential to advance the medicinal use of THC and reduce the risks of its recreational use in some people.
The substance, called d-limonene, is one of the most abundant terpenes, or essential oils, in the cannabis plant, and has shown promise in rodent studies in reducing anxiety behaviors. However, there has been little research on d-limonene or other terpenes in humans.
In a recent study, first published online April 1 in the Journal of Drug and Alcohol Dependence, investigators tested the effects of vaporized d-limonene alone and mixed with THC to examine the anxiety-reducing effects in humans. They found that the addition of d-limonene significantly reduced overall ratings of feeling "anxious/nervous" and "paranoid" compared with THC alone.
As cannabis legalization becomes more prevalent, its use for both medicinal and non-medicinal purposes is expanding rapidly. In recent years, selective breeding of cannabis plants has resulted in strains that contain upwards of 20% - 30% THC, compared with an average of 12% a decade ago.
THC interacts with receptors in the brain to produce feelings of relaxation and euphoria. However, researchers say that when a user is exposed to higher-than-usual doses of THC, the drug can also trigger anxiety, fear, and panic. The study showed that d-limonene can modulate the effects of THC in a meaningful way and make THC more tolerable for both therapeutic and non-therapeutic purposes.
In the study, 20 healthy adults participated in up to 10 outpatient sessions, during which they inhaled vaporized d-limonene alone, vaporized THC alone, vaporized THC and d-limonene together, or vaporized distilled water (as a placebo). The results showed that combining d-limonene with THC significantly reduced subjective reports of THC-induced anxiety.
The researchers plan to continue experimenting with other terpenes alone and in combination with THC to see how they interact with each other, as well as replicate the d-limonene study in larger and more diverse clinical populations.
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