By Pat Anson, PNN Editor

Pick up almost any canned or packaged food in a grocery store and you’ll see a lengthy list of its ingredients, right down to the amount of sodium, fat, vitamins and calories in each serving.

That kind of attention to detail – and truth in advertising -- continues to elude the cannabis industry, according to a new study that found the amount of THC and CBD listed on many medical cannabis products to be wildly inaccurate.

Researchers at Massachusetts General Hospital didn’t test the products themselves, but instead analyzed urine samples from nearly 100 patients who frequently used medical cannabis to treat their pain, anxiety, depression or insomnia. Vaping was the most common form of administration, but patients also smoked or ingested cannabis products purchased at Boston-area dispensaries.   

Laboratory testing showed no CBD metabolites in about a third of the urine samples from patients who said they used cannabis products that were mostly CBD or had equal parts THC and CBD. THC was detected in nearly 80% of those samples, including ones from patients who thought they were only ingesting CBD.

The distinction is important because THC (tetrahydrocannabinol) is the psychoactive ingredient in cannabis that can make users high, while CBD (cannabidiol) is the chemical compound believed to have health benefits.

"People are buying products they think are THC-free but in fact contain a significant amount of THC," says lead author Jodi Gilman, PhD, an investigator in the Center for Addiction Medicine in Massachusetts General’s Department of Psychiatry. "One patient reported that she took a product she thought only contained CBD, and then when driving home that day she felt intoxicated, disoriented and very scared."

About 20% of patients who used a vaporizer had no detectable levels of either THC or CBD in their urine. Researchers think that’s because some vaping devices may not heat cannabis products sufficiently for patients to inhale the active ingredients. THC was more likely to be found in patients who smoked cannabis or ingested it orally.

"A lot of questions about the content of the products and their effects remain," says Gilman. "Patients need more information about what's in these products and what effects they can expect."

The study findings, published in JAMA Network Open, are the latest to show that the actual ingredients in cannabis products vary considerably from their labels. Although 36 states and Washington DC have legalized medical cannabis, there is little consistency in labeling, regulating or testing medical cannabis, as there is for food, supplements and pharmaceutical drugs.

A 2015 study of cannabis edibles sold in California and Washington found that only 17% were labeled accurately. Over half had significantly less CBD than labeled and some had negligible amounts of THC.   

A recent study conducted by the Food and Drug Administration of 147 hemp and cannabis products found that less than half contained CBD within 20% of their label declarations.