Study: Knowledge of Tetrahydrocannabinol and Cannabidiol Levels Among Cannabis Consumers in the United States and Canada


Objective: This study aimed to examine consumer knowledge of tetrahydrocannabinol (THC) and cannabidiol (CBD) levels for usual cannabis products.

Methods: Data are from the International Cannabis Policy Study conducted online in August–September 2018. Respondents included 6471 past 12-month cannabis users, aged 16–65 years, recruited from the Nielsen Global Insights Consumer Panel using nonprobability methods. Respondents were recruited from Canada, which had not yet legalized nonmedical cannabis (n=2354), and US states that had (n=2160) and had not (n=1957) legalized nonmedical cannabis.

Results: Participants reported descriptive THC:CBD ratios (e.g., high THC, low CBD) and numeric THC and CBD levels (mg or %) for products they usually use in each of nine product categories. Few consumers knew and were able to report the numeric THC or CBD levels of their usual cannabis products. For example, only 10% of dried herb consumers reported the THC level, approximately 30% of whom reported implausible values. A greater proportion of consumers reported a descriptive THC:CBD ratio of their usual product, ranging from 50.9% of edible users to 78.2% of orally ingested oil users. Consumers were substantially more likely to report products high in THC versus low in THC for all products except topicals and tinctures, whereas similar proportions reported using products high and low in CBD. Despite some evidence of greater knowledge in legal jurisdictions, knowledge was still low in states with legal cannabis markets.

Conclusions: Consumer knowledge of THC and CBD levels was low, with only modest differences between consumers living in jurisdictions that had and had not legalized nonmedical cannabis. The findings cast doubt on the validity of self-reported cannabinoid levels.


The cannabis market in North America is diversifying in terms of the number of products and modes of administration. Although smoking dried cannabis herb remains the most common mode of administration, use of other forms is increasing, particularly high-potency products, including vape oils and solid concentrates. There is also diversity within product categories, including their levels of tetrahydrocannabinol (THC)1—the primary psychoactive cannabinoid in cannabis that produces impairment. Among commercially available dried herb products, THC levels can range from 1% or less to ∼30%.1–3 Vape oils can have an even greater range—from no THC to more than 90%—while cannabis edibles also vary from several milligrams to several hundred milligrams of THC in a single product.

At the same time, cannabidiol (CBD)-rich products are undergoing significant growth within the North American market.4 CBD is a psychoactive cannabinoid that (unlike THC) does not produce impairment when used alone. Compared with dried herb, CBD is traditionally present in higher concentrations in orally ingested oils and capsules. A broader use of CBD products as natural health products also has emerged in topical creams, often at subclinical concentrations. Anecdotal evidence further suggests that there is an increasing demand for dried herb that has higher levels of CBD or products with balanced levels of CBD and THC. This is likely due to preliminary research suggesting that CBD may have antipsychotic effects and/or moderate some of the impairment produced by THC.5,6

To date, most information on THC and CBD levels is from market scans or sales data in jurisdictions with legal cannabis markets. There is considerable interest in individual-level data to better understand implications of product potency on indicators of problematic use and potential adverse outcomes.7,8

Few studies have examined the accuracy of self-reported THC or CBD levels. One study asked consumers to descriptively categorize the potency (e.g., mild, average, and strong) of their cannabis products and found modest correlations with objectively determined THC concentrations, but to a lesser extent for dried herb compared with hash resin.9 Another study examined subjective estimates of cannabis potency using a scale from 1 (negligible effect) to 10 (incredibly strong).10 Estimated cannabis potency was modestly associated with actual THC concentration among daily users, but not nondaily users, with no differences across product types.

North American jurisdictions that have legalized medical and nonmedical cannabis have regulations that require THC (and in some cases CBD) levels to be labeled on cannabis products. Although the impact of these regulations has yet to be examined, several qualitative and experimental studies suggest that consumers have limited familiarity with THC numbers.11 Few consumers are aware of THC labeling, and consumers struggle to interpret THC numbers as indicators of potency for products such as cannabis edibles.12,13 Consumer difficulties understanding THC may be exacerbated by inconsistent labeling of cannabis products on the illicit market.14

The aim of the current article is to examine self-reported cannabinoid levels among cannabis consumers, with three specific objectives: (1) to examine the proportion of consumers who can report THC and CBD ratios and numeric THC and CBD levels; (2) to compare self-reported THC and CBD levels across each of nine cannabis product categories; and (3) to examine differences in self-reported knowledge of THC and CBD levels across three jurisdictions: US states that had legalized nonmedical cannabis as of August 2018, US states in which recreational cannabis remained illegal (US legal and illegal states, respectively), and in Canada in the year before recreational cannabis legalization.


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