Short communicationHeterogeneity in the composition of marijuana seized in California
Introduction
Fifteen states and the District of Columbia have made allowances for medicinal marijuana, and debate continues about whether it should be regulated and taxed for non-medicinal purposes like alcohol.
Marijuana is a complicated substance containing multiple cannabinoids. Much of the focus has been on delta-9-tetrahydrocannabinol (THC), which is the primary psychoactive substance in marijuana (Iversen, 2007, Pertwee, 2008). There are concerns that marijuana with higher levels of THC may induce anxiety, panic, and psychosis, especially for new and vulnerable users (Di Forti et al., 2009, Hall and Degenhardt, 2009, Hall and Pacula, 2003).
Less attention is devoted to the effects and levels of the other cannabinoids. Cannabidiol (CBD) in particular is relevant as it is thought to reduce anxiety (Crippa et al., 2009, Crippa et al., 2010, Fusar-Poli et al., 2009, Musty, 2005, Karniol et al., 1974, Zuardi et al., 1982) and have antipsychotic properties (Leweke et al., 2007, Morgan and Curran, 2008, Zuardi et al., 1995, Zuardi et al., 2006). Some studies suggest an increasing ratio of THC to CBD may result in more adverse mental health consequences among users (Morgan and Curran, 2008, Potter et al., 2008, Sewell et al., 2009, Smith, 2005), but more research is needed (Room et al., 2010). Learning more about this ratio and how it varies across geography and time may help us better understand mental health and public health consequences of marijuana consumption.
Section snippets
Methods
To shed light on the THC:CBD ratio, we analyze data from 5083 marijuana samples that were seized by law enforcement in California between 1996 and 2008 (mean samples per year: 391; median: 361; minimum: 281; maximum: 540). Of 5556 observations in the original dataset, 432 were removed prior to analysis due to missing values for THC or CBD with an additional 51 removed due to insufficient geographic information. Most samples are from state or local law enforcement, and stem from arrests for
Results
Panel A of Fig. 1 tracks changes in THC levels in seized samples of marijuana in California and shows that median THC potency has increased from 4.56% in 1996 to 11.75% in 2008 (p < 0.001). The increase in THC was far more dramatic in non-border areas (from 4.18% in 1996 to 13.95% in 2008) than in border areas (4.52% in 1996 to 6.84% in 2008). The variation in THC has also increased, with the interquartile range (represented by the size of the box) rising from 2.17 percentage points in 1996 to
Discussion
The composition of the seizures analyzed in this paper may not be representative of the marijuana produced, traded, or consumed in California—especially considering that law enforcement has discretion about what to seize and what to send to the lab. But given the possible health consequences of the THC:CBD ratio, the fact that the ratio is dramatically different for seizures made near the Mexican border versus those further from the border is noteworthy.
While the reasons behind the observed
Role of funding source
This work was supported by NIDA grant R01DA019993, which covered the design and conduct of the study, the management, analysis, and interpretation of the data, and the preparation and review of the manuscript.
Contributors
James Burgdorf originated the concept, wrote the first draft of the paper, and revised it according to the comments of his co-authors. He also conducted the statistical analyses.
Beau Kilmer helped guide the paper conceptually and choose figures for display. He also wrote portions of the paper, directed the statistical testing, and supervised progress.
Rosalie Pacula acquired the data, revised the manuscript for important intellectual content, and supervised project work.
Conflicts of interest
No conflict declared.
Acknowledgements
We thank Tommy Lanier for helping us understand these data, but the views reflected here only reflect those of the authors.
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