Data are cross-sectional findings from the 2019 International Cannabis Policy Study (ICPS) online survey (Hammond et al. 2019), conducted in Canada and the US. Data were collected via self-completed web-based surveys in fall 2019 with respondents aged 16–65. Respondents were recruited through the Nielsen Consumer Insights Global Panel and their partners’ panels. Email invitations were sent to a random sample of panelists, after targeting for age and country criteria. Surveys were conducted in English in the US and English or French in Canada. Respondents provided consent prior to completing the survey and received remuneration in accordance with their panel’s usual incentive structure (e.g., points-based or monetary rewards, chances to win prizes). The study was reviewed by and received ethics clearance through a University of Waterloo Research Ethics Committee (ORE#31330). The full survey includes a comprehensive range of questions assessing cannabis consumption, purchasing behaviors, retail sources, and psychosocial risk factors. The current paper reports findings from an experimental study administered at the end of the ICPS survey, immediately after sections that assessed polysubstance use and opinions of cannabis policies. A full description of the study methods is published elsewhere (Hammond et al. 2020; Goodman et al. 2020a).
Measures
Demographic information
Demographic information included sex, age, ethnicity, highest education level, and perceived income adequacy. See ICPS 2019 survey for item wording (Hammond et al. 2019) and Supplementary Table 1 for response options. Device type used to complete the survey was also collected and included in models to adjust for any effects of screen size when viewing images.
Respondent jurisdiction
Respondent jurisdiction was categorized according to legality of non-medical (recreational) cannabis as of August 2019: Canada (legal), US “legal” states, and US “illegal” states.Footnote 1
Consumption of cannabis edibles
Respondents were asked, “Have you used marijuana in any of the following ways?” followed by a list of modes of administration. Past 12-month consumption of “Edibles/foods” was coded as a binary variable (Yes vs. No/Don’t know).
Knowledge of a standard serving of THC
To assess knowledge of THC serving size information, past 12-month edible consumers were asked, “In places where marijuana is legal, governments use a standard serving of THC. Do you know what the standard serving is [where you live?]” (Yes, No, Don’t know, Refuse). If yes: “How much THC is in one standard serving of an edible [where you live?]”.Footnote 2 Because no jurisdiction has implemented a standard serving greater than 10 mg THC, values of 1–10 mg THC were considered plausible.
Experimental task
Upon conclusion of the main ICPS survey, respondents were shown an image of a cannabis chocolate bar on the screen. Images were displayed according to 1 of 6 randomly assigned conditions, as shown in Fig. 1. A 3 × 2-experimental design was used in which two factors were manipulated: packaging condition (3 levels: whole multi-serving chocolate bar; individual squares; individually packaged squares) and THC stamp (2 levels: THC level stamped on each square vs. no stamp). All packages indicated 10 mg THC per serving and 100 mg THC per package. While viewing the image, respondents were asked, “How many squares of chocolate should someone eat if they want one serving of THC?” (Less than 1 square, 1,2, 3, 4, 5, 6, 7, 8, 9, 10, More than 10, Don’t know, Refuse). To account for jurisdictional differences in serving size (5 vs. 10 mg), responses of “Less than 1 square” or “1 square” were coded as correct.
Data analysis
The 2019 ICPS cross-sectional sample comprised 45,735 respondents; the current sample consisted of 45,504 respondents after excluding 231 who refused to answer the experimental question. Binary logistic regression was used to test the effects of packaging format and presence of THC stamp on odds of responding correctly to the experimental task (Correct vs. Incorrect/Don’t know). The two-way interaction between the packaging and stamp manipulations was tested in a subsequent model. Models were stratified by cannabis consumption in the past 12 months: (1) no cannabis consumption, (2) “any” cannabis consumption, and (3) consumption of cannabis edibles in the past 12 months. Adjusted odds ratios (AORs) and 95% confidence intervals are shown. All odds ratios are adjusted for age, sex, jurisdiction, ethnicity, education, perceived income adequacy and survey device type. Chi-squared tests examined differences between (a) experimental conditions in distribution of the aforementioned covariates and (b) jurisdictions in reported knowledge of standard serving of THC. Analyses were conducted using SAS Studio 9.4.