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. Author manuscript; available in PMC: 2016 Apr 11.
Published in final edited form as: N Engl J Med. 2014 Jun 5;370(23):2219–2227. doi: 10.1056/NEJMra1402309

Figure 1. Increases over Time in the Potency of Tetrahydrocannabinol (THC) in Marijuana and the Number of Emergency Department Visits Involving Marijuana, Cocaine, or Heroin.

Figure 1

Panel A shows the increasing potency of marijuana (i.e., the percentage of THC) in samples seized by the Drug Enforcement Administration (DEA) between 1995 and 2012.50 Panel B provides estimates of the number of emergency department visits involving the use of selected illicit drugs (marijuana, cocaine, and heroin) either singly or in combination with other drugs between 2004 and 2011.51 Among these three drugs, only marijuana, used either in combination with other drugs or alone, was associated with significant increases in the number of visits during this period (a 62% increase when used in combination with other drugs and a 100% increase when used alone, P<0.05 for the two comparisons).