CONTACT Higher and higher - Dr. Christian Thurstone

In the last several months, my colleagues and I have noticed rising levels of THC in the urine of our young patients — but the average increase I present here surprised even us.

THC, which is short for tetrahydrocannabinol, is the active ingredient in marijuana that gives users a high and is chiefly responsible for making the drug addictive (yes, it’s addictive; responsible and respected scientists no longer debate this). In the last 40 years, growers have worked steadily to spike THC levels in marijuana — taking a page from the playbook of Big Tobacco, which was caught spiking nicotine and adding chemicals to make cigarettes more addictive.

Marijuana’s THC levels have increased substantially in the last 40 years. In the 1960s and ’70s, marijuana’s THC levels averaged around 2 percent. Today, they easily exceed 10 percent. In medical marijuana states, including Colorado, where I live, potent strains frequently falling into adolescents’ hands top 40 percent THC.

Then there’s the concentrated form of THC, commonly called hash oil, that is extracted from the plant and added to foods and drinks and inhaled through smokeless vaporizers. THC concentrate can exceed 90 percent.

At the same time THC has risen, so has adolescent marijuana use. Consider this from the University of Michigan’s Monitoring the Future Survey:

  • In 1991, 8 percent of the nation’s high school students reported past-month marijuana use. The past-month use rate reported last year was 15.5 percent.
  • In 1991, 0.9 percent of the nation’s high school students reported daily use. Last year it was 3.5 percent.

With all of this top of mind, my colleagues and I examined the results of approximately 5,000 urinalyses of adolescents treated in a downtown Denver clinic where I practice. The patients were ages 13 to 19.

As you’ll see in the chart below, from 2007 through 2009, the average rate was 358 nanograms per milliliter of urine. This time period immediately preceded the opening of hundreds of marijuana dispensaries in Colorado.

From 2010 through February 2013, the average THC rate registered at 536 nanograms per milliliter of urine. This time period coincides with a boom in access to, and social acceptance of, marijuana in Colorado, where voters in November 2012 approved a constitutional amendment legalizing the drug for recreational use.

Why should we care about this rise in THC rates? What do they mean? Here are some preliminary thoughts as I continue my research:

  • Young people are using marijuana more frequently, or they’re using more potent marijuana, or they’re using more potent marijuana more frequently. I suspect the third option is most likely.
  • When young people report for treatment, their marijuana addiction is more serious. It takes longer to treat them and requires more resources to do so — which means their treatment is more costly.
  • Typically, the more severe the addiction, the poorer the prognosis for recovery.
  • I am increasingly concerned about concentrated THC, which is infused into an ever-growing number of edible products and pushed to users in other smokeless forms that are billed as safer and healthier to use because they don’t involve smoking. My colleagues and I also have found that these smokeless forms of ingesting THC are increasingly popular with young people who are eager to hide their drug use.

It is reasonable now to question how much longer it will be before we see injection use of THC — especially as marijuana is legalized.

UPDATE, Jan. 28, 2015: A state representative in Georgia introduced a bill that would permit injection use of THC outside the bounds of responsible science and the U.S. Food and Drug Administration’s regulatory oversight.


About Chris Thurstone

Dr. Christian Thurstone is one of only a few dozen physicians in the United States who are board-certified in general, child and adolescent and addictions psychiatry. He is Director of Behavioral Health Services at Denver Health and a professor of psychiatry at the University of Colorado, where he conducts research on youth substance use and addiction and serves as director of medical training for the university’s addiction psychiatry fellowship program. You can read more about him here.

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