In the study led by Dr. Ryan Vandrey at John Hopkins University, researchers collected and tested 75 different edible marijuana products representing 47 different brands in the United States.
Of those, only 13 products (17 per cent) were accurately labelled to within 10 per cent of the actual THC content, which is the chemical responsible for most of marijuana's psychological effects.
"It doesn't seem to me that there's any way to reliably know what you're going to get," Vandrey told On the Coast's Gloria Macarenko.
"If everything was consistently under-labelled, then it would be less concerning than what we did find, in that we had under-labelled and over-labelled products, and just a huge variability in terms of what we found."
23% had more THC than labelled
The study found that 60 per cent of the products were over-labelled, meaning they had at least 10 per cent less THC than was advertised on the packaging, while 23 per cent had substantially more THC than was listed on the label.
"If there's too little THC...they're not getting an adequate dose of a drug they think they're purchasing," said Vandrey.
"On the opposite side of that, if it has too much, you're placing the consumer at greater risk for side effects, such as nausea or vomiting, anxiety or paranoia, and in extreme cases hallucinations or acute psychosis."
Vandrey says he wanted to shine a spotlight on the issue of marijuana labelling, because he believes it needs more regulation.
"If we want to legitimately view cannabis as a medicine, it should be regulated. There should be quality assurance and product safety standards, as with other medicines."
New regulations in Vancouver
The study comes only days after Vancouver City Council voted to regulate and license the roughly 100 medical marijuana retailers in the city, making it the first city in Canada to do so.
The new regulations banned the sale of edible marijuana products, with the exception of edible oils. It's a move that Vandrey endorses.
"When you have a medicine such as cannabis packaged in products that are appealing to youth and adults alike, you just increase the likelihood of accidental ingestion," he said.
"We don't have any other medicine that's delivered in a brownie or a cookie."
To hear the full interview with Dr. Ryan Vandrey, listen to the audio labelled: Majority of edible pot products incorrectly labelled, study finds.