Update: After posting this article readers pointed out that it doesn't mention whether the the strains were Indica, Sativa, or Hybrid. In fact, all of these types were studied, but as the researchers noted in their paper, "Indica" and "Sativa" are not "botanical or chemotaxonomical classifications." Rather, they are just used as shorthand to describe their pharmacological effects (i.e., sativas are stimulating and indicas are sedating). As the researchers noted in the paper, "the THC content can be identical between these two classification groups."

Further, many readers mentioned how terpenes are used to differentiate strains. Terpenes are aromatic oils that don't have psychoactive properties, but rather endow a strain with its smell or "flavor." While terpenes can certainly be used to tell different strains apart and some have been noted to have physiological effects (e.g., anti-inflammation), the focus of this research was solely on how cannabinoids are used for cannabis taxonomy.

Walk into any cannabis dispensary in the US and you’ll be presented with dizzying options for getting stoned. When it comes to bud, you can select from strains like “Green Crack,” “Alaskan Thunderfuck,” or “Granddaddy Purp.” Next to these names on the menu will likely be some stats about the concentration of THC and CBD, the two main psychoactive chemicals in cannabis. These numbers offer a sense of standardization and confidence in how that product will affect you.

There’s just one problem: It’s probably bullshit.

As detailed by researchers from the University of British Columbia in a paper recently published in Scientific Reports, many strains of cannabis have almost identical levels of THC and CBD in them. Susan Murch, a chemist at the University of British Columbia, and her colleagues Elizabeth Mudge and Paula Brown examined 33 cannabis stains from five different licensed growers in British Columbia. The researchers then did a chemical analysis of these strains to see the concentrations of 13 known cannabinoids, including THC and CBD.

“The main THC and CBD composition was not different among 24 of the 33 strains we tested,” Murch told me in an email. “However all of the strains have different names from different producers, so for 73 percent of strains, the name does not really mean that they are different based only on the THC and CBD.”

Murch told me that many of the strains she and her colleagues studied were marketed with claims of "quite different" levels of CBD and THC. She said the disparity between the percentage of cannabinoids used for marketing and the actual level of cannabinoids can result from a number of factors, such as the analytical method used, variation across the plant, degradation from storage, or incorrect packaging.

Murch said the packages should acknowledge that there is a range of possible values for the CBD and THC content of the product because it's "impossible to give an accurate value."

"This is also true of most foods," Murch told me. " For example, calories on a label are an approximation rather than an absolute amount but consumers rarely understand that these measures can't be made one very single package, so they are an average across a representative subsample of the product rather than the product itself."

Read More: Weed Strains are Bullshit

During their analysis the researchers also identified 21 previously unknown cannabinoids, a type of chemical that also includes THC and CBD, that may be responsible for the different effects of various weed strains. This suggests that trying to differentiate strains based on just THC and CBD is probably a misguided approach to cannabis taxonomy.

“It is estimated that there are several hundred or perhaps thousands of strains of cannabis currently being cultivated in legal and illegal markets,” the University of British Columbia researchers wrote. “It is possible that chemically identical or very closely related plant material is being sold under several different names by different producers and there is no clear definition of the concept of a ‘strain’.”

Historically, underground breeders with limited access to different types of cannabis plants would breed them together to produce new strains with higher CBD or THC content. Yet due to a lack of formal tracking of this process, many plants with similar genomes ended up being bred, which led to a loss of genetic diversity among the cannabis plants. According to the researchers, this is a likely reason why nearly three-quarters of the strains they analyzed had identical levels of THC and CBD.

“People have had informal breeding programs for a long time,” Murch said in a statement. “In a structured program we would keep track of the lineage, such as where the parent plants came from and their characteristics. With unstructured breeding, which is the current norm, particular plants were picked for some characteristic and then given a new name.”

Read More: We Need More Data On Our Dank

In other words, the lack of information about the origin and chemical composition of most cannabis strains made it difficult to tell whether two strains with different names were really all that different, chemically speaking. Cannabis retailers market bud based on the total amounts of THC and CBD in the flower based on the assumption that the complete chemical composition of the plant can be derived from these values. As the researchers noted in their report, however, “anecdotal evidence suggests that strains with similar THC/CBD content have different effects on human physiology.”

In other words, there’s seems to be far more chemical factors that determine the nature of a high other than CBD and THC. In fact, as the researchers discovered, most strains have nearly identical levels of CBD and THC, so the differences in effects across strains can mostly be attributed to other cannabinoids.