2021 Study: Terpenes Determine Sativa or Indica Labels

Welcome to the first homework assignment for Module 4: Terpenes > Lesson 8: Review for the course Cannabis Foundation: Part 1. This assignment will further teach students about the role of terpenes in the controversial naming system involving indica, sativa, and hybrid and their probable efficacious outcomes.

An October 2021 peer-reviewed research study entitled "Cannabis Labelling is Associated with Genetic Variation in Terpene Synthase Genes" that was published in the journal Nature Plants investigated the potential role of terpenes in determining how cannabis products are labeled and attempted to define the general framework in which cannabis cultivar (strain) efficacy is defined and classified.

The researchers analyzed (via gas chromatography–mass spectrometry and genetic analysis) more than 100 samples of cannabis for their terpene and cannabinoid profiles in an effort to determine if there are genetic differences between cannabis products classified as "sativa" and "indica."

The scientists noted that cannabis is "widely used...and is increasingly being legalized for medicinal and recreational use." Because of this trend toward increased use by larger swaths of society, "it is critical that cannabis's genetic and chemical variation be accurately quantified and communicated," reported the research.

"It is critical that cannabis's genetic and chemical variation be accurately quantified and communicated."

"The vernacular labels Sativa and Indica (not to be confused with the taxonomic names C. sativa sativa L. and C. sativa indica Lam.) are routinely assigned to cannabis cultivars by breeders, retailers, and users to describe a cultivar's morphology, aromas, and/or psychoactive effects," observed the study's authors. "However, it is unclear whether these labels capture meaningful information about cannabis genetic and chemical variation," they added, emphasizing the goal of their study.

The research noted that previous scientific investigations about the genetics of cannabis ("cannabis genomics") have thus far focused mostly on the genetic underpinnings of the major commercial cannabinoids cannabidiol (CBD) and tetrahydrocannabinol (THC). "However, cannabis produces hundreds of aromatic terpenes that drive consumer preference and are frequently associated with Sativa and Indica labels," reported the study.

While most sources attribute the psychoactivity of cannabis almost exclusively to THC (other cannabinoids, including THCV and CBN, also deliver psychoactivity), the study noted that evidence is beginning to emerge that indicates that "a cultivar's terpene profile affects its psychoactive properties."

The study involved analysis of 297 samples of "drug-type cannabis that were quantified for 40 terpenes and cannabinoids using gas chromatography–mass spectrometry." 137 yielded DNA good enough to allow inclusion in the study.

The study involved analysis of 297 samples of "drug-type [THC-rich] cannabis that were quantified for 40 terpenes and cannabinoids." 137 of these samples yielded DNA of a quality good enough to allow full inclusion in the study. The scientists mapped the genetic data analyzed "to a five-point labelling scale ranging from 1 (100% Sativa) to 5 (100% Indica)."

"Principal component analysis of the genomic data showed no clear clustering according to sample labels," declared the study. In other words, the genetic makeup of the cannabis samples did not correspond to whether they were labeled as indica or sativa. "The overall genetic structure explained only 37 percent of the variance in [sativa or indica] labelling," reported the study's authors.

The scientists noted that their results are similar to those of previous studies on the topic.

"Sativa–Indica labels, thus, do not accurately reflect genetic relatedness, which is consistent with previous work," they wrote.

"We determined that pairs of samples with identical cultivar names (for example, OG Kush) were often as genetically and chemically distant from each other as pairs of samples with different names," reported the study.

"We determined that pairs of samples with identical cultivar [strain] names (for example, OG Kush) were often as genetically and chemically distant from each other as pairs of samples with different names."

The scientists noted that their results regarding this lack of labelling logic are "consistent with previous studies indicating that cultivar names were not reliable indicators of a sample's genetic or chemical identity."

The research involved measurement and analysis of 40 terpenes and cannabinoids, of which "12 (30 percent) were correlated with the Sativa–Indica scale." It also revealed that "sativa content was positively correlated with concentrations of [the terpenes] bergamotene and farnesene, which impart tea-like and fruity aromas, respectively."

"Sativa content was positively correlated with concentrations of [the terpenes] bergamotene and farnesene and indica content correlated with the terpene myrcene."

The strongest association, or correlation, found in the study's data was between cannabis samples labelled indica and the terpene myrcene, "whose concentration explained 21 percent of the variation in labelling."

The researchers noted that anecdotal reports by lifestyle (recreational) users attribute myrcene-rich cultivars with a sedative effect and an earthy aroma and that they are "characteristic of Indica cultivars."

"We also observed significant positive correlations between Indica labelling and three sesquiterpenes: Guaiol, γ-eudesmol, and β-eudesmol. Previous scientific investigations found these three terpenes to be associated with cannabis from Afghanistan, which is considered the region of origin for Indica cultivars."

The study explained how previous studies and data gathering efforts "have suggested that the distinction between Sativa and Indica is best explained by differences in the concentrations of specific monoterpenes and sesquiterpenes."

The researchers reported that sativa cultivars are associated with a sweet aroma, whereas products labelled indica involve an earthy scent and that these serve as "key discriminators in a sensory evaluation of cannabis cultivars" and determine how cannabis patients and consumers perceive both the quality and potency of cannabis and cannabis products.

The scientists theorized that cultivators and breeders "have been assigning labels to cultivars primarily on the basis of aroma profiles...rather than genetic ancestry or overall chemical similarity."

The scientists theorized that cannabis cultivators and breeders "have been assigning labels to cultivars primarily on the basis of aroma profiles and purported effects, rather than genetic ancestry or overall chemical similarity."

The study determined that the "primary differences" between cultivars of cannabis labelled indica or sativa "may thus be driven by a small set of [genes] controlling the concentrations of a small number of contrasting aromas."

The study concluded that the labels indica and sativa for loose-leaf, concentrated, and edible cannabis products "poorly captures overall genomic...variation." They suggested that cannabis labelling, in actuality, is more likely "driven primarily by a small number of key terpenes whose concentrations contribute to the characteristic aromas commonly associated with Sativa and Indica."

"A practical classification system consistent with our understanding of the terms Sativa and Indica may be achievable by quantifying a small number of terpenes."

The study's authors noted that the "vernacular labels 'Sativa' and 'Indica' are derived from taxonomic names that were originally used to scientifically categorize plants according to ancestry," but that modern commercial cannabis has redefined them and that they "now probably reflect...genetic variation affecting terpene synthesis."

They surmised that their study results "suggest that a practical and reliable classification system for cannabis that is consistent with a contemporary understanding of the terms Sativa and Indica may be achievable by quantifying a small number of terpenes and/or genotyping genetic markers associated with key cannabis aromas."

Photo courtesy Richard Rose

Hemp entrepreneur and educator Richard Rose has graciously donated some training assets to this article, as found below. To follow the Richard Rose Report, visit the Twitter account or the website.

The following tables and schematic were posted by Rose to the Understanding Cannabis with Higher Learning LV Facebook group on September 18, 2022, in response to a post about this article.

Many experts and thought leaders claim that it is the aromatic terpenes that are produced by cannabis and hemp that determine whether a cultivar may produce uplifting and cerebral effects and be labeled a sativa or whether it delivers relaxation and appetite stimulation and be called an indica. The following table from the Richard Rose Report provides insight regarding the most common terpenes present in cultivars of cannabis and hemp considered indica or sativa.

Image courtesy the Richard Rose Report

The following table applies the same type of terpene analysis to popular strains of cannabis. Typically, myrcene is cited as the most common terpene in cannabis and the one that is present in the largest quantities in many cultivars.

However, one testing laboratory on the East Coast of the United States reported that an analysis of its accumulated testing data revealed that beta caryophyllene, or BCP, was the most common terpene in its client samples, with myrcene taking second place.

Image courtesy the Richard Rose Report

This final chart provides the same data, but in graph form instead of as a table.

Image courtesy the Richard Rose Report

Higher Learning LV would like to thank Richard Rose and the Richard Rose Report for their kind permission to republish their insightful educational resources that help explain the role of terpenes in the popular naming convention of sativa and indica.