Skip to content
When a member asks you tomorrow whether there is anything to the entourage effect, the honest answer until recently was a shrug. Four original studies looked at the same question, and two of them found nothing while two found something. Since 2026 the contradiction can be resolved cleanly, and the resolution teaches you more than the result itself.
The question at stake
Not whether terpenes do anything at all. That is uncontested, and it runs through TRP channels, GABA, adenosine and other targets. The narrow question is this: do cannabis terpenes activate CB1 and CB2 directly, the receptors THC also acts on? Only if that holds is the popular picture of the terpene turning the same dial pharmacologically correct.
Four papers address it head-on. Two from the negative camp, two from the positive camp.
The negative findings of 2019 and 2020
Santiago and colleagues used AtT-20 cells expressing human CB1 or CB2. The readout was the change in membrane potential, that is, a single endpoint. The terpenes tested showed no effect, neither on their own nor together with THC (Santiago et al., 2019).
Finlay and colleagues cast a wider net: five terpenes, radioligand binding with labelled CP55,940 plus a cAMP assay, up to a maximum of 10 micromolar (µM). The conclusion was worded unambiguously: “no data were produced to support the hypothesis that any of the five terpenes tested have direct interactions with CB1 or CB2”. Only beta-caryophyllene showed weak CB2 binding. What is remarkable is the caveat the authors put in the same paper: “this study cannot rule out the existence of an entourage effect for terpenoids” (Finlay et al., 2020).
That caveat was almost entirely lost in how the work was received. Between 2019 and 2021, much of the field treated the entourage effect as settled.
The positive finding of 2021
LaVigne and colleagues tested four terpenes in CHO cells with cAMP and ERK readouts and added the mouse tetrad test, that is, a behavioural model. Alpha-humulene, geraniol, linalool and beta-pinene activated CB1, some of them with additive effects alongside the synthetic agonist WIN55,212. The authors discussed the discrepancy with Finlay openly and named three points: lower concentrations, an assay with only one output, no in vivo model (LaVigne et al., 2021).
The weak point in LaVigne is the concentration. Up to 500 µM in vitro is far beyond what is physiologically plausible.
What Raz does differently
The papers by Raz and colleagues are the methodologically most solid work in this set, for four reasons.
Breadth. 16 terpenes plus mixtures, tested at both receptors with matched concentration ranges. None of the other three papers tests anything like that breadth.
Sensitivity of the readout system. Xenopus oocytes with GIRK current recording. That picks up subtle partial agonists far more reliably than membrane potential or cAMP.
Antagonist verification. Rimonabant for CB1R and SR-144,528 for CB2R abolish the effects completely. Receptor specificity is therefore not inferred, it is shown. That is what makes the finding hard to argue away on methodological grounds. Note that the same series carries a declared conflict of interest, which the section on caution below spells out.
Realistic concentrations. The group stayed at the water-solubility limit rather than pushing beyond it.
The core findings: dose dependent activation at both receptors for most terpenes, with a maximum response at 10 to 60 percent of the THC response, that is, partial agonists. In the same assay, the EC50 values came out comparable to THC or lower (Raz et al., 2026).
Important for context: this is a series of three publications by the same group, not three independent confirmations. 2023 brought the co-application with THC at the CB1 receptor, 2026 the terpenes on their own at both receptors, and also in 2026 the systematic analysis of the interaction with THC. Same working group, same measurement method, same funding. If you count the three papers as three pieces of evidence, you count one too many.
The discrepancy has a methodological explanation
Three factors carry the resolution.
First, concentration. Finlay capped at 10 µM. Several terpenes only become measurably active above that.
Second, assay sensitivity. A membrane potential readout or a cAMP assay simply sees a partial agonist with 20 percent maximum response less well than a GIRK current recording does.
Third, and this is the most interesting point, competition within mixtures. Terpenes given together without THC do less than the sum of their parts, because they compete for the same binding site. Finlay also worked with mixtures in which no single terpene made up more than half. That makes Finlay’s null result for mixtures pharmacologically consistent with the positive result for single substances. These were never contradictory answers, they were different questions.
Together with THC it looks different
This is where the decisive refinement sits, the one added in 2026. The competition applies to terpenes among themselves. Towards THC, many terpenes behave not as competitors but as amplifiers.
The group co-applied terpenes with THC at a ratio of one to ten, so with the terpene as the minority component, the way it occurs in the plant. An isobolographic analysis, which compares the observed effect with the effect you would predict from simple addition, produced genuine enhancement for a subset of the terpenes: borneol, limonene, sabinene, terpineol, alpha-pinene and ocimene at the CB1 receptor, beta-caryophyllene and linalool at the CB2 receptor.
The authors’ reasoning holds up. If terpenes were pure competitors at the same docking site, a weak compound alongside a strong one would have to lower the overall effect. What was observed was mostly the opposite. From that they conclude that a second mechanism is probably also in play, an effect via a different site on the receptor.
Three limitations come with that, and all of them are in the same paper.
One terpene ran the other way. Eucalyptol abolished the THC effect at the CB2 receptor. Humulene and nerolidol showed a trend in the same direction. Not one of these examples appears in the paper’s abstract.
Of eight mixtures, three worked. The group tested eight terpene mixtures modelled on commercial products. Only three measurably enhanced the THC response, one more showed a trend, four did nothing.
The second mechanism is not demonstrated. In the limitations section the authors themselves write that their data do not allow a reliable distinction between an effect via a different receptor site and other explanations. That would take binding studies, mutagenesis and structural models. They did none of it.
Where this finding ends
Everything described so far plays out in a frog egg cell with a receptor built into it. That is the clean place to settle the mechanism question, and it is explicitly not evidence that anything arrives in a human being.
You can now check how far that translation carries, because since 2024 there have been two double-blind studies in humans. Their result comes out mixed, and alpha-pinene of all things, one of the terpenes that showed isobolographic enhancement at CB1 in vitro, changed nothing at a CB1 endpoint in humans. What that means is in the article Two terpene studies in humans, two opposite results.
What this means for how you talk about strains
One thing first, because it decides how you may use the rest: what follows is a description of receptor biology, not a prediction of effect, and it is not a sales argument. Effect claims about specific strains, and any link to availability or distribution, fall under the German advertising ban for consumer cannabis (§ 6 KCanG). Read as description, the selectivity data support statements that go beyond indica and sativa:
- CB1 preferring: alpha-pinene and beta-pinene. They reach the activation level Raz defines as relevant at 0.27 and 0.85 µM respectively, with weak CB2 activation. That threshold is Raz’s own operationalisation and is not clinically validated.
- CB2 preferring: beta-caryophyllene, eucalyptol, limonene, humulene, linalool, sabinene, bisabolol. With an EC50 of 0.01 µM at CB2 against 6.7 at CB1, limonene is the sharpest selectivity finding in the dataset.
- Non-selective: myrcene activates both receptors with similar potency.
What that describes is which receptor a profile addresses, not what a person will feel. CB1 sits mainly in the central nervous system, CB2 predominantly on immune cells and in the periphery. So a pinene-rich chemovar addresses the first receptor population in receptor pharmacology terms, a BCP-rich or limonene-rich one the second. That is a far more precise level of description than any strain story, and it stays a description.
Where caution remains
Four limitations need to travel with this finding whenever you pass it on.
The conflict of interest. Three of the authors are employed by the Bazelet Medical Cannabis Group, which co-funded all three papers in the series. It is openly declared, and the corresponding author Ben-Chaim is academically independent. Even so, independent replication is still outstanding, ideally by the groups that produced the negative findings.
The pharmacokinetics. Which plasma and brain levels are actually reached after inhalation or oral intake is an open question. Raz operationalises an effect level above 0.1 µM THC equivalent as clinically relevant. That is plausible, but it is not clinically validated. The 2026 paper says so explicitly.
The signalling pathway. They only tested Go/i via GIRK. Whether terpenes act differently via beta-arrestin or other cascades is unexplored.
The purity. Some of the terpenes used were markedly impure. Borneol, for instance, was only around 60 percent pure, it is one of the terpenes that showed enhancement, and the paper does not discuss the contamination.
What this means for your club
The statement terpene profiles influence the effect is no longer a pure plausibility argument, it has a mechanism. When you talk to members, the wording that holds up is this: the influence of terpene profiles on effect has been tested in humans, with a mixed result, and so far only for enriched preparations, not for flower. Nothing follows from that about any individual strain or about your own harvest. The reasoning behind it is in the article on the human studies.
The second thing to say to members: more terpenes are not automatically more effect. One terpene ran the other way in the lab, and of eight off-the-shelf mixtures only three worked. What matters is the selection, not the fullness of the profile.
And one strategic point that Raz raises in the closing section, as the authors’ own outlook rather than an established result: in countries with THC restrictions, terpene-only formulations could be a low-threshold alternative. There are no human data on such preparations, and how they would be classified under German and EU law is an open question. Should it hold up, it is highly relevant for regulation in Europe.
[!tip] Take-away
– The original papers on the mechanism question only appear to contradict each other. Concentration, assay sensitivity and competition within mixtures explain the discrepancy.
– Cannabis terpenes act as partial agonists with 10 to 60 percent of the THC maximum response, with EC50 values in some cases comparable to THC or lower in the same assay.
– Terpenes compete with each other for the same docking site. Together with THC, many of them still enhance the effect. That is not a contradiction, these are two different situations.
– Not every terpene helps: eucalyptol abolished the THC effect at the CB2 receptor, and of eight off-the-shelf mixtures only three worked.
– The three Raz papers are one line of evidence from one group, not three independent findings.
– The entire finding comes from cell experiments. Whether anything arrives in a human being is a separate question, and the answer to it comes out mixed (see the follow-up article).
– Wording that holds up: tested in humans, mixed result, so far only for enriched preparations.
Sources
- Santiago et al. (2019), Cannabis and Cannabinoid Research, terpenoids do not modulate THC activity at human CB1 and CB2 · doi:10.1089/can.2019.0016
- Finlay et al. (2020), Frontiers in Pharmacology, terpenoids from cannabis do not mediate an entourage effect at cannabinoid receptors · doi:10.3389/fphar.2020.00359
- LaVigne et al. (2021), Scientific Reports, cannabis sativa terpenes are cannabimimetic and selectively enhance cannabinoid activity · doi:10.1038/s41598-021-87740-8
- Raz et al. (2026), Biochemical Pharmacology 243:117498, selective activation of cannabinoid receptors by cannabis terpenes · doi:10.1016/j.bcp.2025.117498
- Raz et al. (2026), Biochemical Pharmacology 251:118185, synergistic and additive terpene-THC interactions at CB1 and CB2 · doi:10.1016/j.bcp.2026.118185
- Spindle et al. (2024), Drug and Alcohol Dependence, vaporized D-limonene and the acute anxiogenic effects of THC · doi:10.1016/j.drugalcdep.2024.111267
- Kumar et al. (2025), Medical Cannabis and Cannabinoids, individual and interactive effects of alpha-pinene and THC in healthy adults · doi:10.1159/000547014
Note: this article is written for adults and summarises the state of research. It is not advice on consumption or dosing, not a health claim, and not an advertisement for cannabis or for an association.
