AUTHORED BY: GENESTER WILSON-KING, MD FACOG & SARAH RUSSO
Any cannabis user is well aware of the plant’s iconic scent. Often revered and sought after (and sometimes vilified by naysayers) the aroma of cannabis undoubtedly makes an impression. It’s smell comes from terpenes, which are fragrant oils that give all botanicals their unique aromatic signature. The age-old practice of aromatherapy uses scent to evoke various healing benefits with a wide array of applications. Each cannabis variety has a unique blend of terpenes which is responsible for its distinct therapeutic effects.
The “riot of perfumes” as the famous French poet and hashish eater Arthur Rimbaud used to describe the scent of cannabis, includes a dance of over 200 different terpenes. However, only a few of these aromatic oils appear in a concentration great enough for the human nose to pick up on. There are infinite combinations of terpenes, cannabinoids, and other compounds in the cannabis plant, but some are more commonly occurring than others. The terpene profile can vary widely from one type of cannabis to another. [1,2]
For example, Lemon Kush is a well known cannabis variety that is high in limonene, a terpene also found in citrus fruits that is known for its mood-enhancing and antibacterial properties. Blue Dream is rich in myrcene, which is reputed for its sedating, relaxing effects. Sour Diesel is both limonene and myrcene dominant, which may grant both stress relieving and energizing effects. A dynamic array of terpenes can be found in high resin cannabis plants no matter the cannabinoid content (ie CBD dominant, THC dominant, or any ratio of them).
However, just because two cannabis chemovars are sold under the same name (for example “Blueberry”) doesn’t mean they have the same chemical profile. They most often do not. With so many other components in the cannabis plant at play, a variance in effect and experience is unavoidable. However, examining the dominating terpenes via a laboratory analysis may give insight on the type of effect it may have on a user.
The Riot of Perfumes
Cannabis users gravitate towards their favorite variety most often by its smell. People can often reap the benefits of plants simply by inhaling their aroma. This is exemplified in the ancient Japanese practice of “Forest Bathing” where people walking in the woods acquire the relaxing sensation provided by the surrounding pine trees (and their predominant terpene pinene). Many terpenes are volatile and quickly evaporate, filling the air with their aroma. Terpenoids, particularly monoterpenoids, are highly bioavailable via inhalation. 
Terpenes are what give essential oils their smell and grant their healing benefits via scent. Many plants commonly used in aromatherapy such as orange, lavender, rosemary, eucalyptus, pine, and others share terpenes with certain cannabis varieties. For example, a type of cannabis with a “fruity” scent may be dominant in limonene, while earthy scents may come from pinene or beta caryophyllene. Likewise, both lavender and some types of cannabis have higher concentrations of linalool, which may provide an antispasmodic effect.  Check out the next parts of this blog for further specific information on terpenes and their properties and effects.
Where do terpenes come from?
Plants produce terpenes for more reasons than scent. Terpenes provide an evolutionary advantage. These compounds lure beneficial pollinators and protect the plant from predators. They can also prevent fungus and deter disease and pest infestation. Environmental factors influence how a plant grows and the types of terpenes they produce. However, the biochemical profile of terpenes in a given cannabis variety is mostly genetically imprinted rather than influenced by environmental conditions. 
Terpenes are secreted by the resin glands, or trichomes, found in the flowers (or “buds”) of the cannabis plant. The cannabinoids like CBD, THC and others are also produced within the trichomes. Cannabinoids have no scent. It’s the terpene caryophyllene oxide, and not THC, that drug sniffing dogs pick up on when they land on a positive identification for cannabis. 
So how much of cannabis consists of terpenes? Cannabis flowers were previously reported to contain a concentration in a 1-10% range.  However, due to selective breeding, terpene concentrations can be 3.5% or higher in modern chemovars available in the grassroots cannabis supply. 
Many people talk about terpenes, but what about terpenoids? They sound alike, but are they? Terpenes and terpenoids are often used interchangeably, but they don’t mean the same thing. The main difference is that terpenes are hydrocarbons (meaning they only contain hydrogen and carbon). Terpenoids have been denatured by oxidation (drying and curing the flowers) or chemically modified. When people most often speak of the aromatic compounds appearing in cannabis, it is technically referring to terpenoids. [4,9]
Around 50 terpenes are commonly found in cannabis chemovars in North America, but 17 show up most often. Of these, eight of them form the “Terpene Super Classes” which include: myrcene, limonene, linalool, and β-caryophyllene (BCP), α-pinene, humulene, terpinolene, and ocimene. These currently have the most attention for scientific study and selective breeding efforts. 
Terpenes, cannabinoids, and other compounds in cannabis work synergistically to produce what is known as the Entourage Effect. This means that the alliance of plant components work greater together than separately. In 1998 two Israeli researchers, Raphael Mechoulam and Shimon Ben-Shabat, hypothesized that compounds that interact with endocannabinoid system may help to explain how some botanical drugs were often more effective than single, isolated compounds. Even though single molecule is the standard narrative for most pharmaceutical preparations, the case for botanical synergy has gained scientific merit over the years. Various human and animal studies have looked at the entourage effect for conditions such as cancer, chronic pain, and more.
Whole plant cannabis has the benefit of a complex alliance of compounds, while single molecule medications (ex. “CBD-only”) do not produce the same medicinal advantages. For example, clinicians using CBD-dominant cannabis extracts in patients with severe epilepsy demonstrated that they had notable improvement in seizure frequency with lower doses of medication as compared to Epidiolex (a 97% pure, pharmaceutical grade CBD preparation).  This research provides growing evidence for cannabis synergy, and supports ongoing examination on whole plant-based medicines as opposed to single components.
Added terpenes vs naturally occurring
When naturally occurring in the concentrations produced by plants, terpenes are generally recognized as safe (GRAS) by the US Food and Drug Administration. Recent popularity on the benefits of the entourage effect has inspired whole subsets of the cannabis industry devoted to terpenes. As a result, many companies are manufacturing them for use in various products. Some of them contain concentrated amounts, upwards of 20%.  With terpenes, some feel that the more the better. But that isn’t always the case.
Humans often try to replicate the bounty nature provides. This is exemplified in the cannabis industry. Some manufacturers add aromatic compounds to enhance the terpene profiles of cannabis flowers.  To frame the difference between the source of terpenes, let’s break down the categories. The three classes include 1) synthetic 2) food grade botanical-derived (meaning coming from plants other than cannabis) and 3) cannabis-derived.
As opposed to cannabis or other plant-derived terpenes, synthetic terpenes are not found in nature. Synthetic terpenes work to mimic the full aromatic profile of cannabis cultivars. They are usually derived from petroleum products and are not intended for human consumption. They may also contain toxic components. Some companies opt for synthetic options to cut costs. The CO2 extraction process strips away many terpenes, so many companies want to add them back to restore the original aromatic signature. 
Botanically-derived terpenes are generally non-toxic, and many are FDA-approved food additives. However, adding them to cannabis when they are not natural to the plant is not appropriate. It changes the natural genetics of the plant and we don’t know the ramifications. They may make a different impact on the human nose and could be metabolized to other chemicals with distinct pharmacological effects. 
Cannabis-derived terpenes come only from the plant itself. Nature makes cannabis with specific terpene profiles for a reason. In general, the attempt to re-create the odor and flavor profiles of the terpenes that cannabis provides have proved futile.  Many cannabis connoisseurs shun reintroduced terpenes in favor of selective breeding to achieve particular terpene profiles. The yearly High Times Cannabis Cup only allows cannabis-derived terpenes to enter the competition.  In the end, cannabis-derived terpenes would be ideal to preserve the desired psychological and biochemical properties of the plant.
Since terpene specific research is still in its infancy, safety profiles and further research is needed. We need to learn more about how terpenes interact with each other and other chemicals in the plant. Research should also better pinpoint how they provide the unique experience of a particular cannabis variety.
In SummaryFrom age old aromatherapy to modern day extraction methods looking to optimize terpene content, scent will continue to guide users along their healing journey. The unique array of terpenes within cannabis gives an exciting glance at the plethora of opportunities that we still have to discover. Which terpenes are responsible for the specific effects of a given cannabis variety? And what terpenes would be ideal for a given ailment? The nose knows and science will have to catch up. Check out the next section of this terpene series, How Specific Terpenes Work on Pain, Inflammation, Anxiety and More for a breakdown of the scientific research on terpenes for particular conditions.
- Project CBD. (2013). Terpenes and the "Entourage Effect". Accessed on 7/1/2020
- Lee, Martin A. (2014). What Are Terpenes?. Accessed on 7/1/2020
- Erickson, Britt E. (2019). Cannabis industry gets crafty with terpenes. Chemical & Engineering News. Accessed on 7/1/2020
- Russo, E. B., & Marcu, J. (2017). Cannabis pharmacology: the usual suspects and a few promising leads. In Advances in pharmacology (Vol. 80, pp. 67-134). Academic Press.
- Buchbauer, G. (2010). Biological activities of essential oils. In K. H. C. Baser & G. Buchbauer
- Russo, E. B. (2011). Taming THC: potential cannabis synergy and phytocannabinoid‐terpenoid entourage effects. British journal of pharmacology, 163(7), 1344-1364.
- Potter, D. (2009). The propagation, characterisation and optimisation of Cannabis sativa L as a phytopharmaceutical (Doctoral dissertation, King's College London).
- Fischedick, J. T., Hazekamp, A., Erkelens, T., Choi, Y. H., & Verpoorte, R. (2010). Metabolic fingerprinting of Cannabis sativa L., cannabinoids and terpenoids for chemotaxonomic and drug standardization purposes. Phytochemistry, 71(17-18), 2058-2073.
- Terpenes and Testing Magazine. (2019). What Are Terpenes & Terpenoids? Why Do They Matter ?. Accessed on 7/1/2020
- Mechoulam, R., & Ben-Shabat, S. (1999). From gan-zi-gun-nu to anandamide and 2-arachidonoylglycerol: the ongoing story of cannabis. Natural product reports, 16(2), 131-143.
- Russo, E. B. (2019). The case for the entourage effect and conventional breeding of clinical cannabis: no “strain,” no gain. Frontiers in plant science, 9, 1969.
- Weinberg, Bill. (2018). Synthetic Terpenes: Inside the New Industry Shortcut to Flavor. Cannabis Now. Accessed on 7/1/2020
- Morrow, Kenneth. (2020). Terpenes, Hydrosols and Essential Oils: A Primer. Cannabis Business Times. Accessed on 7/1/2020
- Escondido, Nico. (2018) Truth About Terps. High Times. Accessed on 7/1/2020
Genester Wilson-King, MD FACOG is a Board-Certified Obstetrician and gynecologist with over 25 years of clinical experience providing compassionate and research-driven care to patients. After years of working as a full-service OB/GYN, she founded Victory Rejuvenation Center (VRC), a private holistic and preventive medicine practice that provides life-transforming management modalities and customized medicines to patients. She is the Medical Advisor to Treadwell Farms.
As the Medical Director of VRC, Dr. Wilson-King provides services that help her patients age gracefully and achieve holistic well-being. She focuses on plant-based medicine, integrated health, nutrition, supplements, cannabis education, and hormone balance.
Dr. Wilson-King is Co-Vice President of the Society of Cannabis Clinicians (SCC). The SCC is an educational and scientific society of physicians and other professionals dedicated to the promotion, protection and support of cannabis for medical use. Dr. Wilson-King co-authored the Best Practices Guidelines for Cannabis Use in Pregnancy and Breastfeeding, and Cannabis Use in Women – Special Considerations (in progress). She is also on the Board of the Doctors For Cannabis Regulation (DFCR), the first and only national physicians’ association dedicated to the legalization and regulation of cannabis for adults. Advancing the DFCR’s commitment to addressing the disproportionate criminalization of cannabis use among communities of color and the nation’s poor, she regularly provides expert opinions for legal cases involving cannabis.
Dr. Wilson-King is a nationally recognized advocate, clinician, and educator for cannabis and hormone and wellness therapies. She presents on cannabis use in obstetrics and gynecology, hormone therapy for PMS, various stages of menopause, and for applications in nutrition.