Updated: Mar 12
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A June 2021 peer-reviewed research study entitled "A Comprehensive Review of Cannabis Potency in the United States in the Last Decade" that was published in the journal Biological Psychiatry: Cognitive Neuroscience & Neuroimaging investigated the cannabinoid profiles of a large sample of thousands of underground ("legacy market") cannabis samples.
The scientists analyzed "the concentration of seven major cannabinoids, including Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), in illicit herbal cannabis products seized by the Drug Enforcement Administration (DEA) over the last 10 years in the United States."
The study analyzed "cannabis samples received from DEA regional laboratories...by a validated gas chromatography with flame ionization detection method." A total of 14,234 samples of "herbal cannabis" were analyzed over the 10 years prior to the study (between January 1, 2009 and December 31, 2019).
A total of 14,234 samples of "herbal cannabis" were analyzed over 10 years.
"The number of samples received over the last five to six years has decreased dramatically owing to the legalization of marijuana for either medical or recreational purposes in many U.S. states," reported the study.
Overall, the study's results, which involved a very large sample size of cannabis samples confiscated by the DEA, revealed an increase in potency over time. "The results showed that the mean Δ9-THC concentration has increased over the last 10 years, from [about] ten percent in 2009 to 15 percent in 2018 and 14 percent in 2019," reported the study.
The research also reported on the ratio of CBD to THC found in the samples. "The mean Δ9-THC:CBD ratio rose substantially from 24.81 in 2009 to 103.48 in 2017," observed the study. However, it noted that a "decrease in THC:CBD ratio was recorded in the last two years, 54.39 in 2018 and 24.58 in 2019" and that this indicates a production trend that embraces "high-CBD-containing products."
"Our results showed an overall increase in potency of illicit cannabis, from approximately 10 percent in 2009 to approximately 14 percent in 2019."
"Our results showed an overall increase in potency of illicit cannabis, from approximately 10 percent in 2009 to approximately 14 percent in 2019," concluded the study's authors.
They noted that their results "are in agreement with other potency monitoring programs in several European countries." They also concluded that underground cannabis producers and brokers are focusing more on cultivars featuring "higher CBD levels."
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