U.S. Cannabis Potency Update Through 2019: THC Rose, Then CBD Made a Comeback | Research

The takeaway

THC in DEA-seized cannabis continued rising through 2018 (14.88%) but the THC:CBD ratio dropped sharply in 2018-2019, signaling a market shift toward CBD-containing products.

Anyone following the cannabis potency trend over the past two decades, or interested in whether CBD is making a comeback in the market.

24.58
THC:CBD ratio in 2019 — back to 2009 levels after peaking at 103 in 2017

What the researchers found

This third installment from the University of Mississippi's Potency Monitoring Program extended the dataset through 2019, adding 14,234 samples to the two previous reports (RTHC-00039 covering 1995-2014 and RTHC-00049 covering 2008-2017).

THC continued its upward trajectory, reaching 14.88% in 2018 before a slight dip to 13.88% in 2019. The seven major cannabinoids were tracked, providing the most complete chemical profile of illicit cannabis available. But the most notable finding was a reversal in the THC:CBD ratio.

After climbing from 24.81 in 2009 to 103.48 in 2017, the ratio dropped to 54.39 in 2018 and 24.58 in 2019 — returning to 2009 levels. This signaled that CBD-containing products were entering the seized sample pool, likely reflecting the hemp-derived CBD boom following the 2018 Farm Bill. For the first time in two decades, the trend of vanishing CBD reversed.

Why it matters

The potency trend that dominated two decades of data finally showed a wrinkle. CBD's return to the seized-sample profile suggested the market was diversifying beyond pure THC maximization. The 2018 Farm Bill legalized hemp (cannabis with less than 0.3% THC), and the resulting CBD product explosion appeared to be showing up even in DEA seizure data.

This is potentially good news from a public health perspective. If the market shifts toward products with meaningful CBD content alongside THC, the extreme THC:CBD ratios that some researchers link to higher psychosis risk could moderate. But it's too early to know whether this represents a lasting market shift or a temporary blip.

The numbers in context

• THC: 9.75% (2009) → 14.88% (2018) → 13.88% (2019)

• THC:CBD ratio: 24.81 (2009) → 103.48 (2017) → 24.58 (2019)

• 14,234 herbal cannabis samples analyzed

• Seven major cannabinoids tracked

• Fewer samples in recent years due to state legalization reducing DEA seizures

How the study worked

Analysis of 14,234 herbal cannabis samples seized by the DEA and analyzed at the University of Mississippi using validated GC/FID methods. Measured seven major cannabinoids including THC, CBD, CBN, CBG, CBC, THCV, and THCA. Covers January 2009 through December 2019.

Who was studied

N=14,234 cannabis samples seized by the DEA in the US from 2009 to 2019.

What this study cannot tell us

DEA seizure data increasingly underrepresents the overall cannabis market as states legalize. Fewer samples in recent years reduce statistical power. Cannot determine whether the CBD increase reflects actual user preferences or just the presence of hemp products in seizures. Does not capture legal market products, concentrates, or edibles.

How to read the evidence

Large analytical dataset from the same validated program that produced the definitive U.S. potency studies. Strong methodology, limited by reliance on seized samples.

When this study was published

Published in 2021 with data through 2019. The CBD product market has continued expanding since.

The bigger picture

Spanning three reports from this group (RTHC-00039, RTHC-00049, and this one), the dataset covers 1995 through 2019 — nearly 25 years of cannabis potency data. The full arc shows THC climbing roughly fourfold while CBD nearly disappeared, followed by a sudden CBD comeback coinciding with the hemp legalization. Whether the THC ceiling has been reached in herbal cannabis, or whether it will continue climbing in other product forms, remains an open question.

Replication

The findings are in agreement with other potency monitoring programs in several European countries.

Funding

Not reported in abstract.

Conflicts of interest

Not reported in abstract.

Questions still open

Is the CBD comeback a lasting market shift or a temporary artifact of hemp seizures?
Has THC concentration in herbal cannabis plateaued?
Will products with balanced THC:CBD ratios become more popular in legal markets?

Common questions

Is cannabis still getting stronger?

THC peaked at about 15% in 2018 and slightly declined in 2019. But the bigger story was CBD's return — after nearly vanishing from cannabis, CBD-containing products brought the THC:CBD ratio back to 2009 levels.

Why did CBD come back?

The 2018 Farm Bill legalized hemp, triggering a CBD product boom. These products appear to have entered the seized-sample pool, reversing two decades of declining CBD concentrations.

Read the original research

A Comprehensive Review of Cannabis Potency in the United States in the Last Decade.

Biological psychiatry. Cognitive neuroscience and neuroimaging, 6(6), 603-606

Biological Psychiatry is a well-respected journal focusing on the intersection of psychiatry and neuroscience.

View on PubMed ↗Publisher’s paper ↗

Citation

ElSohly, Mahmoud A; Chandra, Suman; Radwan, Mohammed; Majumdar, Chandrani Gon; Church, James C. (2021). A Comprehensive Review of Cannabis Potency in the United States in the Last Decade.. Biological psychiatry. Cognitive neuroscience and neuroimaging, 6(6), 603-606. https://doi.org/10.1016/j.bpsc.2020.12.016