Terpenes May Influence Cannabis Effects, but a Therapeutic “Entourage Effect” Remains Unproven

Terpenes may contribute to the biological effects of cannabis, but current evidence does not establish that they reliably enhance the therapeutic effects of cannabinoids such as THC or CBD. That is the conclusion of a 2024 systematic review, “The Entourage Effect in Cannabis Medicinal Products: A Comprehensive Review”, by researchers affiliated with institutions in Portugal.

The review examined two questions: what physiological effects have been reported for terpenes and terpenoids found in cannabis, and whether studies have demonstrated an “entourage effect” when those compounds are combined with cannabinoids. The researchers organized their search using the PRISMA framework and evaluated evidence from the scientific literature available through December 22, 2023.

Terpenes are aromatic plant compounds that help give cannabis its distinctive smell and flavor. Some also show biological activity in laboratory and animal studies. Myrcene has been associated with sedative or relaxing effects, linalool with sedation and anxiety-related effects, limonene with analgesic and anxiolytic activity, and β-caryophyllene with anti-inflammatory and pain-related effects. Other compounds, including borneol, eucalyptol and valencene, have been investigated for possible anticonvulsant, muscle-pain or cartilage-protective properties.

These findings, however, do not demonstrate that the same effects occur in patients using cannabis products. Many studies examine isolated terpenes at concentrations or by routes of administration that may not reflect typical medical use. A terpene’s activity in a cell culture or animal model cannot by itself show that it produces a clinically meaningful effect when present in cannabis flower or an extract.

The evidence for synergy with cannabinoids is particularly limited. In one example discussed by the review, topical myrcene showed localized anti-inflammatory activity, but combining it with CBD did not produce a statistically significant additive effect. Studies of α-pinene and β-pinene also failed to show certain proposed neuroprotective or anti-aggregation effects in models of β-amyloid-related cellular toxicity, although modest effects on lipid peroxidation suggested that their biological activity may be more specific than broad claims about “neuroprotection” imply.

The review does not rule out interactions between cannabis compounds. Terpenes could theoretically influence cannabinoid effects through pharmacodynamic mechanisms, such as acting on different biological targets, or through pharmacokinetic mechanisms that alter absorption, metabolism or distribution. But the authors found no reliable evidence that terpenes consistently amplify cannabinoid activity at cannabinoid receptors.

Several practical issues make the hypothesis difficult to test. Terpene concentrations vary substantially among cannabis varieties, growing conditions, processing methods and finished products. Many terpenes are volatile and rapidly metabolized, while oral administration can result in low systemic exposure. These factors make it difficult to determine whether the amounts present in a particular product are sufficient to alter the effects of THC or CBD.

The review also highlights a broader problem in botanical medicine: products described as “full-spectrum” or by strain name may differ considerably in their chemical composition. Without detailed chemical characterization and well-controlled comparisons, it is difficult to determine whether differences in patient response are caused by terpene–cannabinoid interactions, cannabinoid dose, other plant compounds, expectations, or unrelated product and patient factors.

That caution is consistent with a 2024 scoping review of the entourage-effect literature, which warned that the term is often used more confidently in cannabis marketing than the evidence allows. Experimental work has also found that major cannabis terpenes did not alter cannabinoid-receptor signaling in the way required to support a simple receptor-level explanation for the effect; see the study of cannabis terpenoids and cannabinoid receptors.

The Portuguese review therefore presents the entourage effect as biologically plausible but unverified, not as an established explanation for why whole-plant cannabis products may differ from isolated cannabinoids. Confirming the hypothesis will require chemically standardized products, clinically relevant doses, pharmacokinetic measurements and randomized clinical trials that directly compare cannabinoids alone with defined cannabinoid–terpene combinations.

For now, individual terpenes remain promising subjects for pharmacological research, but claims that they predictably make medical cannabis more effective should be treated as provisional rather than proven.