For years, the ability of some cannabis strains to render a sedative effect on the user has been explained in the popular media simply as the difference between sativa and indica, and occasionally postulated as being due to the presence of cannabidiol or other cannabinoids. However, evidence is emerging that the effect may actually be due to the interaction between THC and the terpene known as myrcene, which is also present in various other plant species including cannabis’ closest relative, hops.
What Is Myrcene?
Myrcene is a monoterpene (a class of strong-smelling hydrocarbons with the chemical formula C₁₀H₁₆) with an aroma that is described as “herbaceous, resinous, green, balsamic, fresh hops and slightly metallic” and “like floor-cleaner” at higher levels. It is the principle aromatic compound in hops, along with humulene and caryophyllene (together, the three terpenes constitute up to 80 percent of the oil from hop flowers), and is also present in wild thyme, bay, parsley, lemongrass, verbena and ylang-ylang, as well as in cannabis.
Myrcene is widely used in the perfume industry, although rarely as a fragrant compound in its own right; more commonly, it is used as an industrial precursor to various other terpenes including geraniol, menthol, citral and nerol.
Myrcene is the most abundant monoterpene found in cannabis, and in some strains makes up a surprisingly high proportion of the extracted resin. A recent study conducted by researchers at the University of Leiden in the Netherlands investigated the government-licensed strains of medicinal cannabis marketed as Bedrocan, Bediol and Bedrobinol, and found that myrcene was the fourth, third and second most abundant compound present, respectively.
Medical Benefits of Myrcene
Myrcene appears to have various medicinal properties in its own right. More than one study has investigated the compound for its anti-inflammatory and analgesic effects, and one study also demonstrated it to have sedative and motor relaxant effects, along with limonene and citral.
It has also been shown that myrcene, linalool and eucalyptol may exert a protective effect against oxidative cell damage that can cause cancer; that limonene, pinene and myrcene may exert directly tumoricidal effects on cancer cells; and that of four terpenes--pinene, carene, limonene and myrcene--myrcene exerted the strongest anti-invasive effect on metastatic human breast cancer cells.
A toxicity study on rats also determined that extremely high doses of 300mg/kg were necessary to produce adverse effects; while equivalent studies have not been performed on humans, toxicity levels are likely to be comparably low.
How Myrcene and THC Interact
To date, some of the most important research conducted on the interactions between THC and the various terpenes and terpenoids found in the cannabis plant has been provided by Dr. Ethan Russo, former Senior Medical Advisor to GW Pharmaceuticals, the British cannabinoid research company responsible for bringing the drug Sativex to market. In his review Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effect, Russo states that the available data and findings “support the hypothesis that myrcene is a prominent sedative terpenoid in cannabis, and combined with THC, may produce the ‘couch-lock’ phenomenon of certain chemotypes that is alternatively decried or appreciated by recreational cannabis consumers.”
Dr. Russo has also worked in close collaboration with the cannabinoid testing facility Steep Hill Halent to analyze thousands of different cannabis strains and determine their cannabinoid and terpene content. According to an interview with chief research director Kymron deCesare conducted by High Times magazine, 100,000 samples have been tested over seven years, and the indisputable result is that myrcene is the “single most important variable” responsible for producing the so-called “couch-lock” effect. He further states, “Other chemicals may well play minor roles in the couchlock effect, including CBD, CBN and linalool, when they are present in couchlock strains—but they aren’t always present or as influential.”
Interestingly, the presence of high myrcene levels in mango is thought to explain the enhanced effect its consumption is said to have on the effects of consuming cannabis itself. If this is the case, it stands to reason that any other fruit, vegetable or herb containing high levels of myrcene would exert a similar effect.