Half of the cannabis flower products sold in Colorado carry incorrect THC tags, and most of them have a large advantage in psychoactive efficacy.
A comprehensive review of 277 products purchased by 52 dispensaries showed a disturbing pattern: Although the cannabis concentrate has a label accuracy of 96%, traditional flower products cannot meet state standards 44% of the time.
The study, published in a scientific report, was conducted by researchers at the University of Colorado Boulder University, represents the first independent, blind audit of the legal cannabis market label. Its findings raise serious questions about the rapidly expanding consumer protection of the cannabis industry, in which case the accurate dose could mean the difference between therapeutic relief and unnecessary poisoning.
The story of two product types
The team adopted a secret shopper strategy to purchase products from pharmacies in 199 Colorado counties between November 2022 and October 2023. Each sample received only one number before a chemist who had never seen the original label performed a blind test, and no bias would affect the results.
The comparison between product categories proved to be distinct. The average THC content of cannabis concentrate is 71%, showing near-perfect marking accuracy. Of the 99 tests, only four concentrate products fell outside the Colorado 15% accuracy threshold. Flower Products tells another story entirely.
“With the concentrate, I would say Colorado has good label accuracy, but flowers have some real problems with flowers,” observed Cinnamon Bidwell, associate professor of psychology and neuroscience at Cu Boulder and senior author of the study.
Inflation issues
Of the 77 flower products with incorrect labels, 54 exaggerated their THC content, while only 23 underestimated them. This inflation pattern not only prompts random test errors, it points to systemic market pressures that favor higher reporting amounts of effectiveness.
The average flower product contains about 21% THC, a sharp increase from the typical 8% of cannabis in the 1980s. However, the product that labels consistently promise far exceeds the product delivered, with the difference of 5.19% for flowers and 3.20% for concentrates.
These numbers are important because THC efficacy is directly related to health risks. “The THC content has increased significantly, and we know that greater THC may be associated with greater risks, including the risk of marijuana use disorders and some mental health issues,” Bidwell explained.
Hidden chemical complexity
In addition to the THC accuracy issue, the study also found significant gaps in the required label information. Colorado law states that companies report CBD levels but ignore other potentially important compounds. The researchers found that cannabis anti-alcohol (CBG) and cannabis acid (CBGA) associated with anti-inflammatory and anti-anxiety properties are richer than CBD in all product categories.
This regulatory blind spot creates what Bidwell calls a problematic consumer environment: “Focusing on THC on the label can actually cause harm to consumers because it creates an environment that is purchased based solely on THC content. Our data suggests that multiple other cannabinoids should also be reported.”
The science behind the numbers
The research method was analyzed using high-performance liquid chromatography (HPLC) and is considered the gold standard for cannabinoid measurement. Each sample was tested in triplicate to ensure reliability, and the flower product required additional homogenization steps for concentration, which were not required.
This requirement of homogeneity may partly explain the difference in accuracy. Plant materials naturally vary in the cannabinoid distribution, which makes consistent sampling with concentrates more challenging, which undergoes industrial homogenization during production. The team found that despite potential therapeutic properties, 84% of products failed to report the value of six secondary cannabinoids.
Impact on consumer safety
The predictable impact of label differences on titration doses and recreational user expectations in medical patients have real-world consequences. Overestimated efficacy may lead to consumers using more products than expected, while underestimated levels may lead to insufficient therapeutic effects.
Key findings that should involve regulatory agencies include:
- 30.3% flower products exaggerate THC content beyond acceptable limits
- 12.9% low-key potency, which may affect medical dosage
- Despite the richness
- Current 15% tolerance may be too permissible for consumer protection
The study emerged as cannabis legalization spreads nationwide, with Colorado being the regulatory model in other states. The study was funded by the Colorado Cannabis Institute and needed to work with Medpharm Research LLC as federal restrictions prevent university scientists from directly dealing with legal marijuana.
“Cannabis use has complex and broad impacts and we are working to better understand them,” Bidwell stressed. “While this study was conducted, at least we should provide accurate information about the amount of THC in these products.”
The results suggest that protecting consumers in the legal cannabis market may require a rigorous independent testing regimen, especially as high-order products continue to gain market share in the U.S.
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