Most young adults do not understand the advertised levels of tetrahydrocannabinol (THC) in edibles, a new study finds, but the researchers have come up with better way of communicating this information on labels.

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New research examines the efficacy of THC labeling on cannabis edibles.

Research from 2015–2016 shows that, in the United States, almost 10% of the adult population and nearly 24% of youth had used cannabis in the previous year.

Since then, usage has only increased — for instance, one study showed that 33% of teens in grades 9–12 in California had used cannabis in their lives and that most of them had consumed edibles.

Edibles — foods such as cookies, brownies, and candies that contain cannabis — have raised concerns as their popularity has increased in recent years.

Some basis for concern involves marketing that mimics that of regular sweets. Consumers often underestimate the potential effects of edibles — they may not realize how much THC, the main psychoactive element in cannabis, the products contain.

So, new research has investigated the ways in which the THC content of edibles is reflected on labels and how well various labeling systems communicate this information to young consumers.

Prof. David Hammond, of the School of Public Health and Health Systems at the University of Waterloo, in Canada, is the final and corresponding author of the new study, which appears in the journal Drug and Alcohol Dependence.

Prof. Hammond explains the motivation for the study, saying, “Using THC numbers to express potency of cannabis products has little or no meaning to most young Canadians.”

“We’ve known for many years that people struggle to understand the numbers on the back of food packages and cigarette packages. Consumers seem to have equal or even more difficulty with THC numbers, which are used to indicate the potency of cannabis products.”

Prof. Hammond and the team carried out two experiments designed to assess how well different labels convey information about cannabis potency.

To this end, they recruited 870 people aged 16–30 in Canada and conducted an online survey.

In the first experiment, the researchers randomly assigned the respondents to one of three labeling conditions: no label, a label that explained the THC contents in milligrams (mg), or a label that used “doses” of THC per package.

In the second experiment, the team used a traffic light system to label the cannabis products — green signified “low” potency and red signaled “high” potency.

They also tested the effectiveness of no labels, those that advertised THC in percentages, and labels with THC in mg, in the second experiment.

The results revealed that labeling the number of doses per package resulted in the best understanding of a serving of THC — that is, over 54% of the participants’ responses were correct.

Also, the traffic light system made it easier for participants to identify the levels of THC in products. About 85% of respondents correctly recognized products with low levels of THC using this system, and about 86% recognized high THC content.

Prof. Hammond and colleagues conclude:

“Few consumers can understand and apply quantitative THC labeling; in contrast, THC labels that provide ‘interpretive’ information, such as descriptors, symbols, or references to servings have greater efficacy.”

The corresponding study author also notes, “Effective THC labeling and packaging could help reduce accidental overconsumption of cannabis edibles and adverse events, which have increased in jurisdictions that have legalized recreational cannabis.”

Prof. Hammond adds, “New regulations that limit cannabis edibles to a maximum of 10 mg per package are particularly important, given that most consumers do not understand THC numbers.”

“However, the findings suggest that consumers will need easier-to-understand THC information for other products, including oils, concentrates, and dried flowers.”