Recency measures matter: Variability in reported last use of tobacco and marijuana products among a nationally representative study of U.S. young adults.

Introduction: Current use of tobacco and marijuana products is largely defined as use within the past 30-days or more recently. These products are not used in the same manner, frequency, or context especially among young adults who are increasingly at risk for poly-product use. The purpose of this study was to examine patterns of most recent product use across select tobacco and marijuana products.

Materials And Methods: Data used in this study come from a cross-sectional survey conducted among a nationally representative sample of young adults ages 18-34 (n = 1,189) in the U.S. from October-November 2020. Respondents were asked about past product and most recent use of select tobacco/nicotine products (cigarettes, little filtered cigars and cigarillos, large cigars, e-cigarettes, hookah/water pipes) and marijuana products (blunts, e-cigarettes with marijuana, and other products with marijuana).

Results: A high proportion of young adults reported having used at least one tobacco (79.6%) or marijuana (68.6%) products. There is variability in the distribution of most recent use across different tobacco and marijuana users even within the past 3 to past 6 months where nearly one in five users of any product report last use. The average number of tobacco/nicotine products used as well as concurrent marijuana use were lowest when looking at those whose most recent use was within the past 30-days. As the measures of most recent use became more broad, the number of tobacco/nicotine products used increased as did the prevalence of concurrent marijuana use which extended through the past 6-months.

Conclusion: Measures of current use may need to be expanded beyond the past 30-days to include through the past 6-months to better encapsulate usage patterns when considering poly-tobacco and marijuana co-use.