Updated: Aug 13
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A 2023 study entitled "Uncomfortably High: Testing Reveals Inflated THC Potency on Retail Cannabis Labels" that was published in the journal PLOS ONE investigated the label accuracy of a variety of cannabis samples purchased directly from dispensaries, with a focus on consumer advocacy and accuracy in advertising and packaging. "This is the first peer-reviewed study to empirically examine commercial THC potency," reported the study's authors.
"Given the growing economic importance, extensive retail and medical consumption, and proposed medical benefits of Cannabis, it is essential that consumers are provided accurate information about the THC potency of Cannabis that they purchase for consumption," reported the researchers.
Inflated Cannabis THC Potency Study
The study explained that in the United States, marijuana is a Schedule I controlled substance and is defined as the flowering tops from the mature female plants of the botanical species Cannabis sativa L. that contain more than 0.3 percent (one-third of one percent) of the psychoactive cannabinoid delta-9 tetrahydrocannabinol (THC) by dry weight.
The researchers noted that the term marijuana "has historical negative connotations," but that no alternative term for samples of the plant that feature more than 0.3 percent THC has been agreed upon. Technically, the botanical species Cannabis sativa L. produces both "hemp" (which features less than 0.3 percent delta-9 THC) and "marijuana" (producing more than 0.3 percent delta-9). They also reported that attitudes toward legal cannabis have shifted substantially.
Both the medical and adult-use (recreational) cannabis industries encourage "the production of strains with high THC, as price is often contingent on THC potency."
The study reported that, as of July 2022, 37 U.S. states had passed medical cannabis laws, 19 of which also allowed adults to possess and consume marijuana (these numbers have increased since the time of the study). The scientists reported that, economically, cannabis sales have had "significant impacts" and, as evidence, pointed to the $10 billion in cannabis revenue generated between 2014 and 2020 in the state of Colorado alone. Nationally, sales of cannabis in 2020 were $21.3 billion, an increase of 48 percent from 2019.
It explained that all marijuana products, including loose-leaf cannabis samples, are required to report the THC percentage, by dry weight, on the product label (either as a range or as an average). According to the scientists, both the medical and adult-use (recreational) cannabis industries encourage "the production of strains with high THC, as price is often contingent on THC potency."
The Problem: Inaccurate Pot Product Labels
The study explained how various data have indicated that the average THC percentage of loose-leaf cannabis has been steadily increasing since the 1970s. "Recent online media articles addressing THC potency report strains with THC levels ranging from 21–25 percent THC, with some strains exceeding 30 percent."
"The study explained how various data have indicated that the average THC percentage of loose-leaf cannabis has been steadily increasing since the 1970s."
The researchers noted that many reports have questioned the accuracy of cannabis label data. They noted an effort by a group of commercial cannabis laboratories in California to investigate the extent of THC potency inflation. The labs analyzed 150 randomly chosen loose-leaf cannabis samples and found that a whopping 87 percent featured delta-9 THC values that deviated by more than 10 percent from that stated on the label. More than half of the 150 samples featured a deviation from label of more than 20 percent.
Cannabis Lab Shopping
The study reported that a phenomenon has emerged in the cannabis industry that is being referred to as "lab shopping" that involves marijuana cultivators and dispensaries seeking out testing laboratories that provide the most desireable lab results (in terms of delta-9 THC potency) and noted that this is believed to occur in multiple U.S. states. "Prices for both medical and retail flower are driven by THC concentration," reported the research.
The report noted that the cannabis industry has begun to formally recognize inaccurate labelling and lab shopping with a number of lawsuits in California and Arkansas that allege "intentional over-representation of THC concentrations in products has occurred to increase profits." The scientists concluded that this data suggests that there is "a substantial amount of THC potency inflation in Cannabis flower for sale in legal markets" in the United States.
Inflated Cannabis THC Potency Study Results
The current study analyzed 23 cannabis samples that represented a dozen different cultivars (strains). It found a significant difference between reported and observed THC percentage by dry weight.
"Eighteen of 23 samples (78 percent) had a lower observed THC percentage by dry weight than the lowest value reported on the label," noted the study. It stated that the THC percentage displayed on the label of these products was an average of more than 20 percent, whereas actual analysis proved the samples to collectively feature only 15 percent THC.
"On average, observed THC potency was 23 percent lower than the lowest label reported values and 36 percent lower than the highest label reported values."
The study reported that 16 of the 23 samples tested featured actual THC percentages that were 15 percent lower than what appeared on the label. Thirteen of the samples, or 57 percent, were "more than 30 percent lower than the reported value."
The study said that its data demonstrate statistically significant differences between delta-9 THC percentage as displayed on product labels and that observed via its testing and analysis. "On average, observed THC potency was 23 percent lower than the lowest label reported values and 36 percent lower than the highest label reported values, with a maximum percentage change of -57 percent."
Interestingly, the study observed that dispensaries for which it tested two or more samples featured at least one sample where the actual (obsered) THC potency was "more than 34 percent lower than the lowest label reported value." The research concluded that its results "make clear that consumers are often purchasing Cannabis that has a much lower THC potency than is advertised and that this occurrence is widespread."
Inflated Cannabis THC Potency Study Results Conclusions
The study concluded that the increasing legality and greater availability of cannabis make the issue of label accuracy increasingly important. While this study was limited to commercial cannabis samples available from licensed dispensaries in the state of Colorado, it observed that this problem is most likely present in other states. "Given the numerous recent reports and lawsuits questioning THC potency reporting, it is likely that this is an industry wide problem."
"Given the numerous recent reports and lawsuits questioning THC potency reporting, it is likely that this is an industry wide problem."
Like most cannabis-related studies, this one stressed the need for additional research on this topic and in other states, with larger sample sizes yielding more credible data. "Although we have no power to change the current system, we hope highlighting this issue and educating consumers will affect the change needed to remedy inflated potency of flower products," reported the study's authors.
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