There are thousands of individual cannabis types, which people often erroneously refer to as ‘strains’, whereas the preferred term is chemical variety or ‘chemovar’ Each chemovar contains varying concentrations of cannabinoids, terpenes and other constituents with important pharmacological and effects.
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Botanical cannabis is highly inconsistent and variable in its chemical composition. Some authorities describe Cannabis as a single species, while others describe up to four separate species: Cannabis sativa, Cannabis indica, Cannabis ruderalis, and Cannabis afghanica (or kafiristanica). Cannabis likely evolved in Central Asia, native to regions including Afghanistan, Pakistan, India and China. Cannabis species have been found to fall into three general chemotypes (chemical compositions) based on genetically-determined THC:CBD ratios:
- Category I: Relatively high total THC and low total CBD
- Category II: THC:CBD ratios near equal (1:1)
- Category III: Relatively low total THC and high total CBD
Sativa vs Indica
While native Central Asian cannabis is mostly chemotype III (CBD- dominant), emerging commercial cannabis over the last few decades such as currently grown in Washington are more likely to fall into chemotype I (THC- dominant). While there still are biochemically distinct strains of Cannabis, the Cannabis sativa amd Cannabis indica distinction is commonly debated in the laymen’s literature with alleged differences in their constituent combinations and therapeutic effects. Sativa is often described as being more cerebral, uplifting and energetic, whereas indica as being mellow, relaxing and calming. Cannabis Indica plants have higher CBD and lower THC counts.
Terpene concentration studies940 show that “mostly Indica” strains are often dominant in β-myrcene with limonene or α-pinene as the second most commonly present terpenes.
“Mostly sativa” strains were more complex. Some strains were more dominant in terpinolene or α-pinene, while others were dominant in β-myrcene. Terpinolene or ocimene are the second most abundant terpenoids.
There are thousands of individual cannabis types, which people often erroneously refer to as ‘strains’, whereas the preferred term is chemical variety or ‘chemovar’ Each chemovar contains varying concentrations of cannabinoids and other constituents with important pharmacological and modulatory effects. These constituents include the monoterpenoids [myrcene (analgesic, sedating), limonene (anti- depressant and immune-stimulating), pinene (acetylcholinesterase inhibitor alleviating short-term memory impairment from THC) and the sesquiterpenoid beta-caryophyllene (anti-inflammatory analgesic and selective full agonist at the CB2 receptor.
At this time, however, due to the evolution of commercial breeding the distinction between Sativa and Indica, as one expert put it “is total nonsense and an exercise in futility.” One can no longer assess the biochemical content of a given Cannabis plant based on its height, branching, or leaf morphology. Due to the degree of interbreeding and hybridization, currently only a biochemical assay can accurately identify what is really in the plant.
However, no universal standards for laboratory testing protocols currently exist, and there is controversy as to whether all reported results are legitimate. A 2018 study investigated the consistency of reported cannabinoid content of legal cannabis products from state-certified laboratories in Washington. The study documented significant differences in the cannabinoid content reported by different laboratories. It was reported that there is relative stability in cannabinoid levels of commercial flower and concentrates over time. This publication underscores the need for standardized laboratory methodologies in the legal cannabis industry to provide a framework for quantitatively assessing laboratory quality.
THC and CBD concentrations depend not only on the species and strain, but also cultivation, growth conditions, harvesting and storage of the plant. The average contents of THC, CBD, and CBN in dried plant preparations of marijuana confiscated from 1993 to 2008 in the United States were 4.5, 0.4, and 0.3%, respectively, although these contents varied widely. In marijuana resin, commonly referred to as hash or hashish, the average contents of THC, CBD, and CBN are 14.1, 2.5, and 1.9%, respectively. However, in the decade following 2008, various strains and marijuana-based products contain substantially higher contents of these constituents, especially THC which can range upwards of 20-30% or more.
Aside from the increasing number of CBD predominant strains introduced in the market recently, almost all Cannabis currently are high-THC strains. While the strength and ratio of THC and CBD play a large role in the clinical effects of marijuana, a synergy exists between these two components and their combination with other constituents that produce effects that are uniquely determined by the amount and ratios of all the constituents. In addition to THC and CBD, there are other cannabinoids in cannabis including tetrahydrocannabivarin (THCV), cannabigerol (CBG) and cannabichromene (CBC), as well as other pharmacologically active chemical constituents including cannabis terpenoids that impact the clinic effects of marijuana.
Cannabis terpenoids include limonene, myrcene, a-pinene, linalool, b-caryophyllene, caryophyllene oxide, nerolidol and phytol. These terpenoids are derived from a shared precursor with the cannabinoids, and are all flavour and fragrance components common to human diets that have been designated “Generally Recognized as Safe” by the FDA. Terpenoids are quite potent and affect behaviour when inhaled even at very low levels. Terpenoids have unique therapeutic effects that likely contribute to the synergy or “entourage” effects of cannabis with respect to treatment of pain, inflammation, depression, anxiety, addiction, epilepsy, cancer and infections.
In all likelihood, the differences in observed effects in Cannabis are due to their terpenoid content, which is rarely assessed or reported to potential consumers. The sedation of the so-called “indica” strains is often wrongly attributed to CBD content when, in fact, CBD is stimulating in low and moderate doses. Rather, sedation in most common Cannabis strains is attributable to their myrcene content, a monoterpene with a strongly sedative effect that resembles a narcotic. In contrast, a high limonene content (common to citrus peels) will be uplifting on mood, while the presence of the relatively rare terpene in Cannabis, alpha-pinene, can effectively reduce or eliminate the short-term memory impairment classically induced by THC.
This complexity of cannabis constituents and their pharmacologic impact underscores the importance of pharmaceutical medical marijuana in which pharmacologic agents are manufactured with specific doses and ratios which allow for safer titration of dosing to achieve desired clinical benefits.
National Academy of Sciences
The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research
Medical Marijuana – Product Evaluation
- The Cannabinoid Content of Legal Cannabis in Washington State Varies Systematically Across Testing Facilities and Popular Consumer Products – 2018
- Recommended methods for the identification and analysis of cannabis and cannabis products – 2009
- Quality Control of Traditional Cannabis Tinctures – Pattern, Markers, and Stability – 2016
Medical Marijuana –Misc
- A tale of two cannabinoids: the therapeutic rationale for combining tetrahydrocannabinol and cannabidiol. – PubMed – NCBI
- Cannabis and cannabis extracts – greater than the sum of their parts? – 2001
- Pharmacology of Cannabinoids
- Taming THC – potential cannabis synergy and phytocannabinoid-terpenoid entourage effects – 2011
- The Cannabis sativa Versus Cannabis indica Debate – An Interview with Ethan Russo, MD – 2016
- Medicinal Properties of Cannabinoids, Terpenes, and Flavonoids in Cannabis, and Benefits in Migraine, Headache, and Pain – 2018
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