- Researchers have found that many of the cannabis products they tested had lower amounts of THC, or delta-9-tetrahydrocannabinol, than what was listed on the label.
- Cannabis flower refers to the dried flower bud of a female cannabis plant.
- THC is the main intoxicating compound in the cannabis plant.
Product labels, such as those found on food, are designed to help consumers make informed choices about what to buy and what to expect from different products.
Researchers found that many of the products they tested had lower amounts of THC, or delta-9-tetrahydrocannabinol, than what was listed on the label.
Cannabis flower refers to the dried flower bud of a female cannabis plant. THC is the main intoxicating compound in the cannabis plant.
In the study, researchers tested 23 cannabis flower products obtained from 10 recreational dispensaries in Colorado. The products represented 12 cannabis strains.
Testing for the study was carried out by a single certified cannabis testing lab.
The labels on the products listed the THC potency either as a range or as a single number. The researchers said it was not clear if the single number indicated an average of several tests or the result of a single test.
Over 78% of the samples tested had an observed THC potency that was lower than the lowest value listed on the label, researchers found.
In addition, almost 70% of the samples had an observed THC potency that was at least 15% lower than the lowest THC percentage listed on the label.
Across all samples, the observed THC potency was 23% lower on average than the lowest value on the label and 36% lower than the highest label value.
The study was published April 12 in the journal PLoS ONE.
Jamie Corroon, ND, MPH, the founder and medical director of the Center for Medical Cannabis Education in Del Mar, California, who was not involved in this study, cautions that the results are based on a small number of cannabis flower products obtained in one state.
So the results may not apply to other states or other types of cannabis products, such as vape cartridges and edibles.
However, he said this is yet another study that highlights concerns about the accuracy of cannabis product labels. Corroon has previously raised this issue with hemp-derived cannabidiol (CBD) products.
Tory Spindle, PhD, an assistant professor of psychiatry and behavioral sciences at Johns Hopkins Medicine in Baltimore, was not surprised by the results of the new study.
In a study published last year in
Many products also contained higher levels of THC than allowed by the federal Agriculture Improvement Act, they found.
In contrast with their study, which tested CBD products obtained online and at national retailers, the new study used cannabis products obtained at retail dispensaries.
“There is a sense that products that you purchase from a dispensary would have better oversight,” said Spindle. “Clearly, this study would suggest that’s not necessarily the case.”
As of April 2023, 38 U.S. states and the District of Columbia allow medical use of cannabis products, and 21 states and the District of Columbia allow adult non-medical use. However, at the federal level, cannabis remains an illegal substance.
Among this patchwork of cannabis laws, a wide variety of products are available legally across the country.
However, the average THC potency of products tested in the new study was about 15%.
The lower average THC potencies found in testing studies compared to market surveys suggests a mismatch between cannabis flower products and their labels.
“It’s possible that our current understanding of cannabis potency has been inflated due to mislabeled products and inaccurate certificates of analysis,” said Corroon.
“[Results such as these] further underscore the need for accurate and reliable labeling,” he added, saying that this is needed for all cannabis products, including edibles and vape-cartridges.
The legal cannabis industry has exploded as different states have legalized the drug.
According to Forbes the sale of recreational and medicinal cannabis was expected to reach $33 billion in 2022.
Other research has found that different cannabis testing laboratories can give different potency results on the same flower product, which may contribute to some of the label problems.
Some industry experts have suggested that “lab shopping,” where cannabis growers and dispensaries seek out laboratories that give them more favorable results, may be driving some of label inaccuracies.
”Based on conversations I’ve had with industry over the years, ‘lab shopping’ is a real-world phenomenon. However, I don’t know how widespread it is,” said Corroon.
“In many states with regulated cannabis programs, enforcement resources are limited, which can make it difficult to effectively prevent this practice,” he added.
Consumers are already aware of the problem with cannabis product labels — lawsuits recently filed in Arkansas and California allege that certain cannabis companies and testing labs are overstating the THC content of products.
Spindle said the results of the new study are concerning for a number of reasons.
For example, people may be paying more for cannabis flower products than they should be, because the price is based on the THC potency listed on the label.
In addition, “from a medical cannabis user perspective — or even someone using recreationally — if the label is not accurate, then it makes it difficult to know [how much THC] you’re going get from administration to administration,” he said.
Corroon agrees. “From a medical standpoint, accurately estimating the dose of THC used by patients to treat different conditions can be a challenging task,” he said.
For example, “when individuals inhale smoked or vaporized cannabis, they typically adjust the dose instantaneously based on how they feel,” he said.