Changes in Cannabis Potency Over the Last 2 Decades (1995-2014): Analysis of Current Data in the United States

Biol Psychiatry. 2016 Apr 1;79(7):613-9. doi: 10.1016/j.biopsych.2016.01.004. Epub 2016 Jan 19.


Background: Marijuana is the most widely used illicit drug in the United States and all over the world. Reports indicate that the potency of cannabis preparation has been increasing. This report examines the concentration of cannabinoids in illicit cannabis products seized by the U.S. Drug Enforcement Administration over the last 2 decades, with particular emphasis on Δ(9)-tetrahydrocannabinol and cannabidiol.

Methods: Samples in this report were received over time from materials confiscated by the Drug Enforcement Administration and processed for analysis using a validated gas chromatography with flame ionization detector method.

Results: Between January 1, 1995, and December 31, 2014, 38,681 samples of cannabis preparations were received and analyzed. The data showed that although the number of marijuana samples seized over the last 4 years has declined, the number of sinsemilla samples has increased. Overall, the potency of illicit cannabis plant material has consistently increased over time since 1995 from ~4% in 1995 to ~12% in 2014. The cannabidiol content has decreased on average from ~.28% in 2001 to <.15% in 2014, resulting in a change in the ratio of Δ(9)-tetrahydrocannabinol to cannabidiol from 14 times in 1995 to ~80 times in 2014.

Conclusions: There is a shift in the production of illicit cannabis plant material from regular marijuana to sinsemilla. This increase in potency poses higher risk of cannabis use, particularly among adolescents.

Keywords: CBD; Cannabinoids; Cannabis sativa; Gas chromatography with flame ionization detector; Potency; Δ(9)-THC.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Cannabinoids / chemistry*
  • Cannabis / chemistry*
  • Chromatography, Gas
  • Humans
  • Illicit Drugs / chemistry*
  • Substance Abuse Detection
  • United States


  • Cannabinoids
  • Illicit Drugs