Initial validation of a brief assessment of cannabis demand among young adult college students

Abstract

Behavioral economic models of addiction posit that cannabis’s reinforcing value (demand) is linked to use. The Marijuana Purchase Task (MPT; Aston et al., 2015) quantifies demand by assessing hypothetical cannabis consumption across escalating price points. Indices generated from MPT performance include intensity (i.e., amount consumed when free), Omax (i.e., peak expenditure), Pmax (i.e., price at peak expenditure), elasticity (i.e., degree that consumption decreases as price increases), and breakpoint (i.e., cost suppressing consumption to zero). Cannabis demand is linked to engagement in risky behaviors and cannabis use disorder (CUD) symptomology. However, the length of the MPT makes repeated assessment of state-dependent changes in cannabis demand difficult, which limits clinical utility. Brief assessments of alcohol and cigarette demand exist that measure intensity, Omax, and breakpoint. Thus, the aim of the current study was to develop and validate a brief assessment of cannabis demand. College students (N=211, Mage=19.91, SD=1.44; 63% Female; 56.4% Non-Hispanic Caucasian) who reported past-month cannabis use ≥3 times completed an online survey. Participants completed the MPT, a 3-item brief assessment of marijuana demand (BAMD) assessing intensity, Omax, and breakpoint, and measures of demographics, cannabis use frequency, cannabis-related negative consequences, CUD symptomology based on DSM-5 criteria, and cannabis craving. Convergent validity was examined via bivariate correlations of demand indices on the BAMD, MPT, and cannabis outcome measures. Divergent validity was assessed via independent samples t-tests to examine whether demand indices on the BAMD differed based on the presentation or absence of CUD. A one-way between-subjects ANOVA with planned comparisons was tested to compare effects of CUD severity (mild/moderate/severe) on BAMD demand indices. Intensity, Omax, and breakpoint were significantly correlated across the MPT and BAMD (rs=.30 – .79, ps<.01). Intensity, Omax, and breakpoint on the MPT and BAMD were significantly correlated with current cannabis craving, CUD severity, and cannabis-related negative consequences (rs=.18 – .48, ps<.05). Only intensity and Omax were significantly correlated with cannabis use (rs=.16 – .43, ps<.01). Individuals with (versus without) a CUD reported significantly greater intensity and Omax (ps< .01), but not breakpoint, on the MPT and BAMD. There were significant effects of CUD severity on B-MPT demand indices (ps<.05). Planned comparisons revealed that individuals with a moderate or severe CUD had significantly elevated intensity, Omax, and breakpoint on the BAMD compared to individuals with a mild CUD. Only breakpoint differentiated individuals with a moderate and severe CUD. This is the first study to validate a brief assessment of cannabis demand. Consistent with prior alcohol and tobacco research, the BAMD espoused convergent validity with the MPT and divergent validity by differentiating individuals with and without a CUD and along the CUD severity continuum. Thus, the BAMD may be a useful tool to assess links between specific indices of cannabis demand and clinically-relevant outcomes over time and in real-world settings. However, given the rise in novel cannabis products with different modes of administration and varying potencies, future research should examine whether demand differs based on these factors. Further, replicating these findings among more diverse populations is essential.