Are There Limits to the Range of Possible Cannabinoid Ratios in Plants?

March 12, 2020
Abstract / Synopsis: 

Strikingly similar results have been reported from a wide range of studies on the ratio of tetrahydrocannabinol (THC) to cannabidiol (CBD) concentrations in strains of cannabis. Whether the source has been legalized markets in the west, medical markets in the U.S. and Canada, or collections from law enforcement and researchers, three easily distinguishable types of plant have consistently been found: THC-dominant strains (with less than 1% CBD); CBD-dominant strains (less than 1% THC); and balanced strains with comparable concentrations of both substances. Another consistent finding of these studies, carried out in a variety of laboratory settings, is a positive correlation between THC and CBD levels in those plants that can make substantial quantities (>1%) of each. The correlation between THC and CBD quantities in these varied populations suggests that there is a fundamental property of the plant that makes some combinations impossible, for instance, >15% THC and also >5% CBD. Such results have never shown up in published data sets of carefully, consistently tested samples, but those were all relatively small collections. A much larger data set has been released by the state of Washington (140,000 flower samples), and this has been scrutinized for evidence of consistently propagated strains with higher than a 2-to-1 ratio.

As cannabis emerges from the shadows of the prohibition era into the mainstream wellness market, two corresponding forces are changing the way the product is discussed and evaluated: health-conscious consumers are looking for specific benefits from the product, not simply a “high;” and the simple classifications of products that have been traditionally provided to consumers are being replaced by sophisticated biochemical and genetic evaluations.

Cannabis products today are generally sold under colorful strain names, often with combination names that refer to the predecessor strains from which the new strain was bred. In addition, cannabis products are frequently categorized as being of indica or sativa origin, or more likely as being a blend with a certain percentage of indica and sativa.

For consumers who are looking for specific health effects from cannabis, it is important that they are confident that repurchasing a product with the same, or related, strain name will give them the same positive experience they are seeking (and, conversely, that by avoiding other strain names they will not repeat a negative experience). As more and more sophisticated data is collected on the contents of cannabis products and careful investigation made of the reliability of names and classifications, it is becoming increasingly clear that our current naming systems for cannabis products is inadequate to reliably guide purchasers who are seeking reproducible experiences.

Indica and Sativa Do Not Give Meaningful Guidance on Cannabinoid Content

The terms indica and sativa date back more than 200 years. Originally they described the differences in plant shape and leaf pattern, but more recently they have been used as shorthand terms for cannabis varieties that were considered more sedating or more stimulating. After generations of cross-breeding, and with abundant opportunity for misidentification and mislabeling, the validity of these terms as a means of distinguishing expected effects has been called into question. Over the past few years, a number of rigorous studies of the biochemical properties of plants have reached the conclusion that the traditional indica and sativa terminology are not reliable indicators of the property that is of greatest interest to consumers: the cannabinoid profile.

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About the Author

Thomas A. Coogan, PhD, is an Academic and Research Liaison with the New Jersey Cannabis Industry Association. Direct correspondence to: [email protected]


How to Cite this Article

T.A. Coogan, Cannabis Science and Technology 3(2), 32–39 (2020).