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Cannabis Got Stronger Again: THC Doubled From 2008 to 2017 and Concentrates Exploded

RTHC-019762019Chandra, Suman; Radwan, Mohamed M; Majumdar, Chandrani G; Church, James C; Freeman, Tom P; ElSohly, Mahmoud A
ObservationalModerate evidence
The takeaway

Average THC in seized cannabis rose from 8.9% to 17.1% between 2008–2017, while concentrates surged to 55.7% THC and the THC:CBD ratio hit 104:1.

Anyone using cannabis today who wants to understand just how much the product has changed, or researchers contextualizing older studies.

55.7%

Average THC in cannabis concentrates by 2017, up from 6.7% in 2008

What the researchers found

Picking up where ElSohly's earlier analysis left off, this study tracked another decade of cannabis potency data from the University of Mississippi's monitoring program. The trends not only continued — they accelerated. Average THC concentration nearly doubled from 8.9% in 2008 to 17.1% in 2017. The THC-to-CBD ratio, already high, climbed from 23:1 to 104:1.

But the bigger story was concentrates. Hash oil samples (now called cannabis concentrates) went from 0.5% of seized samples to 4.7%, and their average THC concentration skyrocketed from 6.7% to 55.7%. The seizure data also revealed a structural shift: fewer samples overall were being seized as states legalized, but what was seized was dramatically more potent.

European data from the Netherlands, UK, France, and Italy showed parallel trends — this wasn't a U.S.-only phenomenon.

Why it matters

This is the sequel to the 1995–2014 potency study (RTHC-00039), and the trajectory only steepened. The average joint in 2017 carried roughly twice the THC of one from 2008 and four times what was available in the mid-1990s. Meanwhile, concentrates — barely a factor a decade earlier — emerged as a distinct product category testing above 55% THC.

The vanishing CBD is the quiet part of this story. A THC:CBD ratio of 104:1 means modern cannabis has essentially zero CBD relative to THC. If CBD does moderate THC's psychiatric effects (as some research suggests), the market has systematically eliminated that buffer.

The numbers in context

• Average THC: 8.9% (2008) → 17.1% (2017)

• THC:CBD ratio: 23:1 (2008) → 104:1 (2017)

• Concentrate THC: 6.7% (2008) → 55.7% (2017)

• Concentrate share of seizures: 0.5% (2008) → 4.7% (2017)

• Total samples analyzed: 18,108

How the study worked

Analysis of 18,108 cannabis samples seized by the DEA and analyzed at the University of Mississippi's Potency Monitoring Program using validated GC/FID methods. Covers January 2008 through December 2017. Also reviews potency monitoring data from European programs for cross-national comparison.

Who was studied

N=18,108 cannabis samples analyzed over 10 years, US and Europe.

What this study cannot tell us

Limited to DEA-seized samples, which increasingly underrepresent the market as legalization reduces the illicit supply. Fewer samples were available in later years. Cannot determine whether users adjust consumption to compensate for higher potency. European data came from different monitoring programs with varying methodologies.

How to read the evidence

Large analytical chemistry dataset (18,108 samples) with validated methods. Reliable for measuring potency trends, but limited to seized (not purchased) samples.

When this study was published

Published in 2019 with data through 2017. Legal market products have since pushed concentrate potency even higher.

The bigger picture

Between the two potency monitoring studies (RTHC-00039 and this one), the picture spans 1995 to 2017 — THC went from about 4% to 17%, a roughly fourfold increase. And this data ends before the fully mature legal market, which has pushed concentrates even further. Any cannabis research conducted on low-potency products has limited relevance to what people actually use today. That's not an argument for or against cannabis — it's a data integrity issue for the entire field.

Replication

Other potency monitoring programs in Europe have documented similar increases in THC concentrations.

Funding

Supported by the National Institute on Drug Abuse (NIDA).

Conflicts of interest

Not reported in abstract.

Questions still open

  • Do users of high-potency cannabis consume less per session, or do they simply intake more THC?
  • Has the rise of concentrates changed the risk profile for cannabis-related psychiatric events?
  • Would mandatory CBD content minimums in legal products change health outcomes?

Common questions

How strong is cannabis now compared to 10 years ago?
Average THC roughly doubled from 8.9% in 2008 to 17.1% in 2017. Concentrates went from 6.7% to 55.7% THC. And these numbers predate the fully mature legal market.
What happened to CBD in cannabis?
It essentially disappeared. The THC:CBD ratio went from 23:1 in 2008 to 104:1 in 2017, meaning modern cannabis has virtually no CBD relative to its THC content.

Read the original research

New trends in cannabis potency in USA and Europe during the last decade (2008-2017).

European archives of psychiatry and clinical neuroscience, 269(1), 5-15

The European Archives of Psychiatry and Clinical Neuroscience is a reputable journal focusing on psychiatric and neurological research.

View on PubMed ↗Publisher’s paper ↗

Citation

Chandra, Suman; Radwan, Mohamed M; Majumdar, Chandrani G; Church, James C; Freeman, Tom P; ElSohly, Mahmoud A. (2019). New trends in cannabis potency in USA and Europe during the last decade (2008-2017).. European archives of psychiatry and clinical neuroscience, 269(1), 5-15. https://doi.org/10.1007/s00406-019-00983-5

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