Do Terpenes Give Cannabis Its Scent? Think Again! New Research Shows There's More to What Meets The Nose

When most people think of cannabis aroma, their minds immediately jump to terpenes. These fragrant compounds, found in a variety of plants, are often credited with giving cannabis its distinctive scent profile. However, Dr. Adie Rae, a cannabis and psychedelic research PhD and Assistant Scientist at Legacy Health, has discovered that terpenes are just one piece of the puzzle, and aroma plays a much larger role in cannabis’ effects than we previously believed.

We interviewed Dr. Rae to learn more about her research and the findings from her paper The Nose Knows: Aroma, But Not THC Mediates The Subjective Effects of Smoked and Vaporized Cannabis Flower.

Benefit Is Key

First, we wanted to know why people should be looking beyond terpenes at all when considering cannabis’ aroma. Dr. Rae gave a good analogy to help us understand, “You can think of this as a features vs. benefits situation. For example, when I’m buying a pair of shoes, I’m not looking at the tech specs that tell me the foam density, or what specific kinds of plastics they’re using to construct them. I’m simply shopping for the benefit of comfort,” says Dr. Rae. 

“Our research says to take the same approach with cannabis: the chemical features might contribute to the aroma, but at the end of the day the individual features don’t really matter. The aromatic benefit should be a consumer’s focus.”

In the paper The Nose Knows, Dr. Rae concluded that the pleasant aroma of cannabis is a predictor of pleasant subjective effects, perhaps even more so than cannabinoids as previously believed. If true, this is a bombshell of a revelation. 

Dr. Rae expanded on this idea that aroma is paramount, “We hypothesize that this effect is driven by expectancy,” she says. She explains that when a person has no lab information or information on THC levels, but they can see and smell the flower, that can make all the difference. “When a person smells a nice aroma, this probably primes their brain for a pleasant experience,” Says Dr. Rae. “It’s like a self-fulfilling prophecy. Similarly, when they smell a boring or unpleasant aroma, they’ve set a trajectory for a less pleasant experience.”

Still, while this may sound rather placebo in effect, it’s worth considering the active chemical compounds responsible for the pleasant smell that elicits the pleasant effect, and as it turns out, these chemical compounds go beyond terpenes and cannabinoids.

“Volatile sulfur compounds, esters, ketones, and aldehydes are a few notable categories,” says Dr. Rae, listing chemical compounds that she says previous literature has revealed to be just as important as the aforementioned terpenes. “We have some ongoing studies to see how these compounds might contribute to specific aroma characteristics, like “citrus” notes. Those results will be published in 2025, so stay tuned!” She reports.

How Do Terpenes Factor In?

One does have to wonder however, if terpenes aren’t the be-all-end-all of aroma as previously thought, what role do they play?

“Frankly, we may never know the answer to this question,” says Dr. Rae. “There are so many terpenes to study individually, and then of course, we’d have to study them all in combination with cannabinoids like THC. When consuming cannabis, we’re exposed to very low doses of terpenes. At those doses, it would be very surprising for them to have a major impact on any physiological function. The only peer-reviewed study that has looked at this in humans used a 2:1 ratio of THC:limonene. Sure, at this high dose, limonene had an anti-anxiety effect, but that huge dose of limonene would never exist in a natural product. Plus, if you’re smoking flower or storing it for a long time before you consume it, many of the terpenes will completely break down or evaporate, never making it inside of your body.”

It’s safe to say that this really flips what the world thought was known about terpenes, and it raises a whole host of new questions. One such question that immediately came to mind was, if aroma is such an important aspect of cannabis quality, how can something that is largely considered subjective, such as smell, be quantified into an objective review when conveying feedback about a cultivar’s scent to someone who hasn’t smelled it?

How To Talk About Aroma

In other words – how do we accurately communicate aroma?

“Subjectivity can’t be completely overcome, but there is some rhyme and reason to it,” says Dr. Rae. “Our data shows that the more pleasant an aroma is, the more consensus there is. Let’s use perfume as an analogy: almost everyone who smells Tom Ford’s Black Orchid loves it. It’s a highly desirable aroma, and there is a lot of consensus about that fact. Now, let’s consider a Victoria’s Secret perfume or Axe body spray – a bit more polarizing, right?”

“So, I think researchers have an important task ahead of them,” Dr. Rae continues. “We need to define which kinds of aromas belong in the Tom Ford category, and which belong in the body spray category. That way, a consumer shopping online could at least filter out the body spray types – and to be fair, some people will always love body spray, and that’s just fine… for them! At the end of the day, it truly does come down to the consumers smelling for themselves. This is why deli-style retail sales are so important, and mandatory closed packaging does such a disservice to the consumer.”

When asked if there will be a way to capture aroma as a data point for cross-state or country trade, Dr. Rae replied that her team’s research is trying to solve this problem, “at least in part.”

“Our first step is to develop a consensus-based lexicon – a list of words that describe the aroma characteristics of cannabis and hemp. Sure, there are plenty of words floating around out there on the internet on various sensory ‘wheels,’ but these tools were not developed using all the best practices of genuine sensory science. We think that this is an important first step, which is indeed an objective way to communicate about a product’s sensory features.”

The goal aligns with other notable organizations focused on best practices, such as The International Cannabis and Hemp Standards (ICHS), who have developed a common language and quality grading standards for cannabis material. Complementarily, companies like Cannafax have developed accessible tools to implement the ICHS into active quality grading of material. Undeniably, the industry has found the need for a consistent way to speak about cannabis is an essential part of operating. It only makes sense that as the science behind cannabis aroma evolves, so too will the language used to discuss it.

“When our studies are done, a wholesale distributor could say something like, ‘I have 20 kilos of Type I citrus in stock, and another 30 kilos of Type I herbal,’” Dr. Rae says as an example. “A consumer could walk into a retailer expressing their preferences ‘I prefer berry over citrus.’”

The Future of Cannabis Commodity and Research

But Dr. Rae’s vision does not stop there. She foresees a future with not only the right words to succeed but also the right training. “In the near future, cannabis producers, distributors, and retailers will all undergo sensory training, which is extremely common for other food and beverage commodities. People who work in coffee or orange juice distribution get extensive sensory training so that they all agree on what ‘sweet’ or ‘nutty’ means.”

So where does that leave the average consumer in a dispensary, who doesn’t necessarily have access to sensory training? Will their nose be able to guide them? Dr. Rae believes it will be a matter of desirability. “Everyone will need to make their own decision with their own nose, but there will indeed be some ‘Tom Ford’ flowers,” says Dr. Rae.

With such interesting research and compelling new ways to consider aroma, we had to ask Dr. Rae what she found to be the most surprising aspect of her research into cannabis aroma. 

“The degree to which people are still hung up on terpenes,” Dr. Rae replied without skipping a beat. “You wouldn’t believe the backlash we’ve experienced based on people’s pre-conceived notions about the ‘importance’ of terpenes. This is a perfect example of dogmatic thinking. The thing about science is that by design, it is always tearing down our previous belief systems to build a more accurate understanding of our universe. At one time, we collectively thought the sun revolved around the Earth. Now, through observation, we know how it really works. It’s simply a matter of humility to let go of previous beliefs and be open to the ever-evolving evidence.”

Thanks to research like Dr. Rae’s, we can continue to push the boundaries of our understanding of this fascinating plant. By remaining open to new information, we can better harness the power of cannabis and its beneficial effects on humankind.

Fortunately for us all, Dr. Rae’s research continues. Her team’s experiential research was largely based on cultivars with high THC, and she’d love to explore the lower potency range. “How low can we go – in terms of THC percentage – without losing desirable subjective effects? When people are blinded, how do they respond to CBG and THCV dominant cultivars?” Muses Dr. Rae. “There is a lot more work left to do!”

Rae Lland

Writer

Rae Lland is a writer, journalist, and former editor for Weedist and The Leaf Online. She is known most notably for her long-time tenure as a writer for Leafly, in addition to being featured in other online cannabis publications and print editions of Cannabis Now Magazine. Follow her on Instagram @rae.lland or LinkedIn.