A small sample of marijuana sold legally in Colorado found that most products contained much less tetrahydrocannabinol (THC) – the main psychoactive component of the plant – than was listed on the packaging.
“We know it’s happening and everyone’s talking about it, but no one has put scientific rigor behind it,” says Anna Schwabewho did research at the University of Northern Colorado but is now at the cannabis company 420 Organics.
She and her colleagues obtained 23 samples from 10 Colorado dispensaries and tested them for THC concentration in a private lab. Colorado, like other US states that have legalized recreational marijuana, requires dispensaries to have the ability to label products based on testing from third-party laboratories.
They found that the samples were an average of 23 percent less potent than those at the low end of the range listed on the label. More than half the samples were more than 30 percent less potent.
“People are paying for a product and they’re not getting it,” Schwabe says. For medical marijuana users, this could mean someone is not getting the proper dosage, she says.
Discrepancies can come from laboratories sampling different parts of a plant, or using different testing equipment or methods, say Eric Paulson at the Infinite Chemical Analysis Laboratory in California. But he says there is a clear incentive for laboratories to overcapacity. He says buyers often pay more for marijuana with higher THC content, and dispensaries can choose the labs that give them the best numbers.
In 2022, Paulson’s Company analyzed of more than 150 samples from dispensaries in California, and found that nearly all had potencies that differed by more than 10 percent from the label. He says his company has lost customers by reporting accurate, low-potential results. “All manufacturers know which labs to go with.”
Stephen Goldman Kaycha Labs, a national testing company, says the capability is especially prized in new markets like California, Oregon and Michigan, and the Colorado results don’t surprise him. “Can labs do better in general? Absolutely,” he says.
new scientist The study contacted three dispensaries that appeared to have received the samples based on the license numbers listed. Two did not respond and one declined to comment.