Packing cannabis, pouring alcohol: Validating a free-pack assessment among college students using cannabis.

Objective: Long-standing challenges in quantifying cannabis use make assessment difficult, potentially complicating attempts to minimize harm. Our study investigated how accurately undergraduates who use substances estimate amounts of alcohol through a behavioral pouring task. We also aimed to validate a free pack assessment in which participants similarly estimated amounts of cannabis. We further examined how estimations related to consequences and protective behavioral strategies (PBS). Methods: Participants completed a free pour task and a modified free "pack" task to measure out and estimate quantities of alcohol and cannabis, and self-reported use, problems, PBS, and social context (N = 264; Mage = 19.2, 67.10% Female, 46.20% White). Results: Both tasks indicated high rates of misestimating amounts. Over 80% of the sample misestimated alcohol and cannabis amounts by more than 10%. Students typically underestimated the actual amount of alcohol that they poured, but the trend was opposite for cannabis. Discrepancies in packing joints decreased as quantity-specific cannabis PBS increased, but increased with more frequent cannabis use. Both alcohol and cannabis PBS decreased their respective consumption and negative consequences. Conclusions: A considerable proportion of young adults inaccurately estimate quantities, which is related to negative outcomes. Discrepancies are associated with problems, and interventions may benefit from targeting improvements in accuracy to prevent future harms and enhance protective strategies for specific substance use methods. (PsycInfo Database Record (c) 2021 APA, all rights reserved).