Understanding the Entourage Effect in Cannabis

It is a common misconception that THC is the only active ingredient in cannabis. Cannabis contains hundreds of different compounds, and the varying concentrations of these are thought to be part of why products feel different, for example uplifting rather than sleepy. This proposed interaction is called the entourage effect.

The word "proposed" matters. Parts of the idea have support, and parts are still being tested. This article sets out what the entourage effect is, what the evidence shows so far, and what it means for a prescribed product. It is general information, not individual medical advice.

Key takeaways

• The entourage effect is the proposed idea that cannabinoids and terpenes shape each other's effects, so a whole product acts differently from THC on its own.
• It is a hypothesis with some supporting evidence, not an established fact.
• THC percentage is not a measure of how well a product will work for you. Two products with the same THC can feel quite different, and many patients do better on a lower strength than a higher one.
• Indica and sativa labels are an unreliable guide to what a product contains.
• Your doctor chooses a product on its full analysis, not on its name or its THC number. What helps most is telling your doctor what does and does not suit you.

What the entourage effect is

The term was first used in 1998 by researchers studying the body's own cannabinoid system, who found that compounds with no activity of their own could boost the activity of one that did [1]. In 2011 the neurologist Ethan Russo applied the idea to the cannabis plant, proposing that its cannabinoids and terpenes work together, so that the whole plant acts differently from any single compound taken out of it [2].

In practice, "entourage effect" is the name for a question: why do two products with the same THC content feel different? The proposed answer is the rest of their makeup, meaning the other cannabinoids and the terpenes.

What the evidence shows so far

The evidence is mixed, and it helps to take it in parts.

CBD and THC. This is the best-studied interaction. A 2019 systematic review of 16 studies found that CBD reduced some of THC's effects, such as anxiety and psychosis-like experiences, in several studies, but not consistently across studies, and with no clear pattern by dose [3]. A 2023 randomised trial gave 46 people vaporised cannabis with the same THC and four different amounts of CBD, and found that CBD did not significantly change THC's effects on memory or psychotic symptoms at any of the doses tested [4]. CBD may change how THC is experienced, but it cannot be relied on to do so.

Terpenes and THC. Most of the evidence on terpenes comes from laboratory and animal studies. One of the few human trials, published in 2024, found that vaporised limonene reduced the anxiety and paranoia that a high dose of THC caused in 20 healthy adults, without changing THC's other effects [5]. It is an encouraging result, but it is one terpene in one small trial.

Individual terpenes. The effects reported for each terpene come from early and largely preliminary research, and the therapeutic role of individual terpenes is not well established. Our guides to myrcene, linalool, caryophyllene, limonene and pinene set out what the research on each does and does not show.

Why THC percentage is a poor guide

If THC were the only thing that mattered, the product with the highest THC percentage would always work best. It does not. Two products with the same THC percentage can feel quite different, and many patients do better on a lower strength than a higher one. A higher percentage mostly means more THC in each dose, which raises the chance of side effects such as anxiety as well as the chance of relief.

The labels on products are no more reliable. Laboratory analysis of commercial cannabis has repeatedly found that a product labelled indica can have a terpene profile indistinguishable from one labelled sativa [6,7]. Our guide to what indica means covers that research.

Full-spectrum products

Full-spectrum products keep more of the plant's cannabinoids and terpenes, rather than isolating a single compound. If the entourage effect holds, that could make them behave differently from an isolate. It has not been shown that full-spectrum products work better for any particular condition, and they can contain small amounts of THC, which matters for roadside and workplace drug testing.

What this means for your prescription

• Your doctor chooses the product on its full analysis. That means its THC and CBD content and, where the supplier publishes it, its terpene profile, rather than its name or its THC number.
• You do not need to pick terpenes yourself. The terpene information you are given is there to help you describe what does and does not suit you.
• Keep notes. How a dose felt, how long it lasted, what it helped with and any side effects. That is what lets your doctor adjust the product, the dose or the form. Our guide to preparing for a follow-up appointment covers what to note.
• Ask for the test report if you want it. The certificate of analysis for the batch lists the terpenes, and you can ask your pharmacy for it.

If you vaporise flower, the temperature changes the balance of what reaches you. Our article on terpenes and vaporiser temperature explains how, and why temperature is part of the dose.

Frequently asked questions

Is the entourage effect real?

It is a hypothesis with some supporting evidence. Some interactions between cannabinoids have been shown in people, but the results are mixed, and most of the evidence on terpenes comes from laboratory and animal studies.

Does a higher THC percentage mean better relief?

No. THC percentage is not a measure of how well a product works. Many patients do better on a lower strength, and a higher strength raises the chance of side effects.

Should I choose a product by its terpenes?

Not on your own. Your doctor chooses a product on its full analysis. What helps is telling them what has and has not suited you.

References

1. Ben-Shabat S, Fride E, Sheskin T, et al. An entourage effect: inactive endogenous fatty acid glycerol esters enhance 2-arachidonoyl-glycerol cannabinoid activity. Eur J Pharmacol. 1998;353(1):23-31.
2. Russo EB. Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects. Br J Pharmacol. 2011;163(7):1344-1364.
3. Freeman AM, Petrilli K, Lees R, et al. How does cannabidiol (CBD) influence the acute effects of delta-9-tetrahydrocannabinol (THC) in humans? A systematic review. Neurosci Biobehav Rev. 2019;107:696-712.
4. Englund A, Oliver D, Chesney E, et al. Does cannabidiol make cannabis safer? A randomised, double-blind, cross-over trial of cannabis with four different CBD:THC ratios. Neuropsychopharmacology. 2023;48(6):869-876.
5. Spindle TR, Zamarripa CA, Russo E, et al. Vaporized D-limonene selectively mitigates the acute anxiogenic effects of Δ9-tetrahydrocannabinol in healthy adults who intermittently use cannabis. Drug Alcohol Depend. 2024;257:111267.
6. Watts S, McElroy M, Migicovsky Z, et al. Cannabis labelling is associated with genetic variation in terpene synthase genes. Nat Plants. 2021;7(10):1330-1334.
7. Smith CJ, Vergara D, Keegan B, Jikomes N. The phytochemical diversity of commercial Cannabis in the United States. PLoS One. 2022;17(5):e0267498.