UC Irvine

This dissertation investigates the multifaceted relationship between cannabis and tobacco co-use across three distinct but interconnected studies, employing geospatial, behavioral, and longitudinal epidemiologic methods. The overarching objective is to better understand the mechanisms that drive co-use patterns and their implications for both tobacco and cannabis.The first study utilizes geospatial analysis to examine the clustering of cannabis and tobacco retailers across Los Angeles County. Results from generalized additive models indicate a significant spatial association between cannabis retailer locations and proximity to tobacco retailers, particularly in neighborhoods characterized by higher proportions of racial/ethnic minorities, young adults, and unlicensed cannabis retailers. These spatial patterns may contribute to disproportionate exposure to cigarillos used for blunt smoking in vulnerable communities. The second study applies a modified case-crossover design to evaluate whether blunt use acutely increases the likelihood of subsequent unmodified little cigar or cigarillo (LCC) use. Drawing on data from a diverse sample of co-users, findings reveal that concurrent blunt use significantly elevated the odds of LCC use within the same hour, a behavior referred to as "blunt chasing." Contextual factors such as outdoor settings and time of day were also associated with increased co-use risk, highlighting the importance of situational cues in co-use behavior. The third study uses Markov Transition State Modeling to estimate short-term and projected cessation probabilities among chronic cannabis users who also used cigarettes, electronic nicotine delivery systems (ENDS), or multiple tobacco products. Findings indicate that poly-tobacco users exhibited the lowest cessation rates, followed by cigarette users, whereas ENDS users had the highest likelihood of cessation but were also prone to transitioning into cigarette or poly-tobacco use. Together, these studies underscore the complexity of cannabis-tobacco co-use, illustrating how structural, situational, and behavioral factors interact to sustain tobacco use. The findings emphasize the need for multifaceted, co-use–specific interventions and policies that account for the spatial accessibility of retail environments, short-term behavioral risk, and longitudinal cessation trajectories among cannabis users.