Using Real Time Data to Examine the Impact of Product Characteristics on Young Adult ENDS Use - PROJECT SUMMARY Electronic nicotine delivery system (ENDS) use patterns and product characteristics (e.g., flavors, device types, nicotine concentration) have fluctuated since their introduction into the US marketplace. In this fluid environment, traditional assessment methods often fall short of capturing real-time and real-world use behaviors, especially for young adults. All of the large, nationally representative studies (e.g., PATH) that provide substantial evidence on patterns of ENDS use and product characteristics used among this vulnerable population rely on self-report measures that ask respondents to recall behaviors and describe product characteristics over extended periods of time (e.g., past 30-days). While the data are useful for surveillance, these methods likely overgeneralize patterns in the onset and progression of ENDS use like, polytobacco use, progression, and cessation; and thereby prevent any valid understanding of how product characteristics within FDA's regulatory authority influence these behaviors. Innovative, real-time and real-world methods, measures, and assessments are critically needed to better understand the impact of ENDS product characteristics on ENDS use behaviors and abuse liability. Our objective is to improve and advance the overall rigor of tobacco regulatory research using a novel measurement method. In this longitudinal study, we propose to use traditional survey methods with Ecological Momentary Assessment (EMA) to overcome limitations noted above that likely undermine tobacco regulatory science. We focus on young adults (ages 18-25) as a priority population, as ENDS use in the U.S. is highest among this age group and lifelong patterns of tobacco use are established during young adulthood. A national sample of young adult (ages 18-25) ENDS users (n=350; 50% exclusive ENDS users, 50% dual users) will participate in a 30-day EMA measurement “burst” every 6 months, as well as a survey to better inform FDA's understanding of behaviors and abuse liability. Our overall hypothesis is that EMA measures of ENDS characteristics, use behaviors, and abuse liability (e.g., nicotine dependence) will more accurately capture details relevant to the FDA compared to the traditional survey, thereby strengthening the state-of-the-science that informs its regulatory authority as it relates to ENDS. We will examine both short-term (i.e., day to day) and long- term changes (i.e., Wave to Wave) in ENDS use behaviors, including frequency of use, flavors and devices used, progression, cessation, and polytobacco use. We aim: 1) To assess concordance between traditional survey and real-time EMA measures of ENDS use behaviors (e.g., progression, dual/poly use, and cessation), ENDS product characteristics (e.g., flavors, device type, nicotine concentration) and abuse liability (e.g., dependence) among young adults, 2) To examine the effect of ENDS product characteristics on tobacco use behaviors among young adults, and 3) To examine the effect of changes in ENDS product characteristics on dependence and use behaviors among young adults.