New research in the Journal of the American Medical Association finds medical-marijuana edibles in Seattle are inaccurately labeled for potency. Most often, the edibles contain far less THC than advertised.

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Yet another sampling of marijuana products has found inaccurate labeling of potency.

A new article in the Journal of the American Medical Association (JAMA) reports that all but one of the 23 edible products bought in Seattle medical-marijuana dispensaries last year were improperly labeled. Most of the baked goods, beverages and candy contained less THC than their labels said. THC is the main psychoactive chemical in marijuana.

Previous research, including by The Seattle Times, has found similar inaccuracies in medical marijuana and legal recreational pot. But the JAMA study’s lead author said his research was more rigorous than work by news organizations and others.


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“If we want to recommend cannabis as medicine, patients should expect reliability and consistency in what they’re buying. The failure to do so is an injustice to the consumer and puts patients at risk,” said Ryan Vandrey, lead author and associate professor at Johns Hopkins University School of Medicine.

Risks amount to more than the severe anxiety New York Times columnist Maureen Dowd wrote about experiencing with an edible snack in Colorado. They can also include vomiting, hallucinations and psychosis, Vandrey said.

The JAMA study examined edibles after they were purchased in three cities: Seattle, San Francisco and Los Angeles.

Seattle products were “severely overlabeled,” Vandrey said. “These were products that contained far less THC than advertised,” he said.

One edible contained less than 1 percent of what it was supposed to have, he said. Eight of the other 22 samples contained between just 3 and 33 percent of the labeled THC content.

Vendrey’s article does not name the three Seattle dispensaries at which products were bought last fall. He and co-authors decided not to call out individuals, he said. “Instead we wanted to point out the problem as a whole and encourage regulation.”

Their decision might have been different, he said, if they had found only a couple of manufacturers at fault. But because they found inaccuracies across a range of products, he didn’t want the study to be “construed as promoting or degrading certain companies.”

Samples from San Francisco, as in Seattle, tended to be weaker than labeled. Los Angeles samples tended to be stronger than labeled. In all, just 13 of the 75 samples from the three cities tested by Vandrey were accurately labeled, meaning the key chemical content of tested samples was within 10 percent of their labeling; 17 samples were stronger than the label indicated and 45 were weaker.

The inconsistencies point to two main problems, Vandrey said. Because all pot remains illegal under federal law, medical-marijuana products lack the consistent dosing found in drugs regulated by the Food and Drug Administration. Medical-edibles manufacturers are not careful enough in their testing, Vandrey said. A likely problem, he said, is that they’re testing a corner of a cookie or brownie, not the entire edible. For his research, Vandrey said products were crushed or mixed and tested with high-performance liquid chromatography equipment.

Vandrey said he had no idea if manufacturers were deliberately mislabeling products to encourage sales.

Washington state and California do not require dispensaries to test their products. But Washington does require its legal recreational retailers to test products at state-certified labs for potency. “If you ask me, that’s backward,” Vandrey said of Washington’s current rules.

Under changes made by the state Legislature this year, medical marijuana will require the same testing for potency as recreational weed in Washington state.