Exploring survey methods for measuring consumption quantities of cannabis flower and concentrate products

Abstract

Background: Researchers need accurate measurements of cannabis consumption quantities to assess risks and benefits. Survey methods for measuring cannabis flower and concentrate quantities remain underdeveloped.Objective: We examined "grams" and "hits" units for measuring flower and concentrate quantities, and calculating milligrams of THC (mgTHC).Methods: Online survey participants (n = 2,381) reported preferred unit (hits or grams), past-week hits and grams for each product, and product %THC. Quantile regression compared mgTHC between unit-preference subgroups. Hits-based mgTHC calculations assumed a universal grams-per-hit ratio (GPHR). To examine individualized GPHRs, we tested a "two-item approach," which divided total grams by total hits, and "one-item approach," which divided 0.5 grams by responses to the question: "How many total hits would it take you to finish 1/2 g of your [product] by [administration method]?"Results: Participants were primarily daily consumers (77%), 50% female sex, mean age 39.0 (SD 16.4), 85% White, 49% employed full-time. Compared to those who preferred the hits unit, those who preferred the grams unit reported consuming more hits and grams, higher %THC products, and consequently, larger median mgTHC (flower-hits mgTHC: 32 vs. 91 (95%CI: 52-67); flower-grams mgTHC: 27 vs. 113 (95%CI: 73-95); concentrate-hits mgTHC: 29 vs. 59 (95%CI: 15-43); concentrate-grams mgTHC: 61 vs. 129 (95%CI: 43-94)). "Two-item" and "one-item" approach GPHRs were similar and frequently 50% larger or smaller than the universal GPHR.Conclusion: Allowing respondents to choose "hits" or "grams" when reporting cannabis quantities does not compromise mgTHC estimates. A low-burden, one-item approach yields individualized "hit sizes" that may improve mgTHC estimates.

Keywords: Cannabis; THC; measurement; quantity; survey.

Figure 1.

Survey items used to assess grams and hits quantities for cannabis flower and concentrates.

Figure 2.

Consumption quantity differences between unit preference subgroups. Each of the four graphs compares the distribution of quantities reported by those who prefer the hits unit to the distribution of quantities reported by those who prefer the grams unit. A hollow circle indicates a participant’s reported quantity, and a solid black horizontal line indicates the median reported quantity. Comparing the two median values within each of the four graphs demonstrates that those who prefer the grams unit reported larger quantities – regardless of the unit (hits or grams) used to report those quantities. * indicates statistically significant (p<0.05) difference between median values. Green graphs (left side) display reported flower quantities; orange graphs (right side) display reported concentrate quantities. Graphs in the top row display reported number of hits; graphs in the bottom row display reported number of grams.

Figure 3.

Milligrams THC (mgTHC) calculated using hits or grams responses for different unit preference subgroups. Each of the four graphs compares the mgTHC distribution of those who prefer the hits unit to the mgTHC distribution of those who prefer the grams unit. Graphs on the left display mgTHC estimates calculated using participants’ reported number of hits; graphs on the right display mgTHC estimates calculated using participants’ reported number of grams. A hollow circle indicates a participant’s reported quantity, and a solid black horizontal line indicates the median mgTHC estimate. Comparing the two median values within each of the four graphs demonstrates that mgTHC estimates among those who prefer the grams unit are larger than mgTHC estimates among those who prefer the hits unit – regardless of the unit (hits or grams) used to calculate mgTHC estimates. * indicates statistically significant (p<0.05) difference between median values. Green graphs (top row) display mgTHC estimates based on reported flower quantities and potencies; orange graphs (bottom row) display mgTHC estimates based on reported concentrate quantities and potencies.

Figure 4.

Within-subject difference of grams-per-hit ratio (GPHR) estimates: two-item approach estimate minus one-item approach estimate. Two GPHR estimates were calculated for each participant using different methods. Graphs in Figure 4 display the distribution of values obtained by subtracting each particiant’s two GPHR estimates. The distributions are primarily centered around zero – suggesting that the two methods yield similar GPHR estimates.