The increase in use of e-cigarettes in adolescents is a major public health concern that must be addressed. Research studies showed some e-cigarettes contained varying amounts of nicotine and sever cancer-causing chemicals. The purpose of this quantitative, cross-sectional study was to assess the perception of harm (dependent variable) from using e-cigarettes and being exposed to state and school-based antitobacco programs (independent variable) and to determine if the association was modified by socioeconomic status or area of residence. Attitude-social influence-self-efficacy theory was the chosen theory for research and suggests that attitude, social influence, and self-efficacy variables can be persuaded via specific health promotion activities. Texas students enrolled in 6th to 12th grade of an eligible school who voluntarily consented to participate and received written authorization from a parent were included. Nearly half of participants out of N=9,239 adolescents considered e-cigarettes very dangerous, yet more than half reported using the device. Ordinal logistic regression was used to determine the relationship between the independent and dependent variables. The results concluded that though majority of adolescents perceived e-cigarettes as harmful, exposure to state and school antitobacco programs are not completely effective at discouraging use. The findings of the study may provide potential impact for positive social change for adolescents and tobacco cessation by increasing understanding of what factors are associated with increased/decreased perception of harm. Results of the study may encourage public health professionals to create and disseminate tailored antitobacco educational information including school and state activities and resources.

Electronic nicotine delivery systems emerged during the 2010s as a novel way to consume (i.e., vape) nicotine. Public health authorities became concerned that vaping could cause nicotine-naïve youth to begin using tobacco products and that a new generation of youth could become tobacco-dependent. Though millions of youth have vaped, authorities' fears about a new generation of youth tobacco dependence has not materialized. A more recent concern is nicotine vaping’s potential effects on cannabis use and the use of other substances. An increase in cannabis use among some adolescent groups and young adults could be because of nicotine vaping’s rise. Additionally, cannabis can be vaped, so transitioning from nicotine vaping to cannabis vaping may be easier than transitioning from nicotine vaping to other forms of cannabis use. Furthermore, nicotine product use was historically associated with later use of cannabis and other substances; this trend may be renewed with the advent of nicotine vaping. To date, most studies on the associations between nicotine vaping and cannabis/other substance use are cross-sectional, so more longitudinal evidence is needed. If evidence suggests that nicotine vaping does affect the use of cannabis and other substances, specifying a mechanism would help with developing potential interventions and with testing the validity of total effects. The overarching goal of this dissertation is to advance evidence of nicotine vaping's potential harmful effects on youth and young adults, which could be used to support interventions aimed at reducing the burden of nicotine vaping's outcomes. First, I conducted a systematic review in which I examined the extent to which confounding, measurement errors, and loss to follow-up could alternatively explain reported longitudinal effects of nicotine vaping on cannabis use or other substance use. I also identified studies that tested effect modification and mediation. This systematic review revealed that nicotine vaping likely increases the risk of subsequent cannabis use and other substance use for up to 24 months. It also revealed that some studies evaluated effect measure modification, while no study assessed mechanisms. These observations suggest that future studies should assess long-term effects on initiation and evaluate potential mechanisms. Second, I evaluated whether nicotine vaping affected the initiation of cannabis and other substances over a six-year period among adolescents as they age into adulthood. Results suggested that nicotine vaping had harmful effects on both outcomes over the six-year period. I also found evidence that nicotine vaping's harmful effects in later years appeared stronger than in earlier years; the absence of age effects suggest the absence of cohort effects. Furthermore, I found that effects appeared stronger among individuals who had a history of non-vaping tobacco product use than among individuals without a history of non-vaping tobacco product use, suggesting that tobacco use is key to nicotine vaping's harms. Finally, I evaluated possible mechanisms of the effects based on a theory that I developed from prior empirical literature and behavioral theory. I posited that nicotine vaping caused deviant peer affiliation, which caused conduct problems and subsequently, the outcomes. I found no evidence that three conduct problems (considered together) were mechanisms of the effects. Future studies of mechanisms can reveal potential intervention targets, lead to studies of other potential mechanisms, and help test the validity of total effects. This dissertation achieved its goal of advancing evidence that nicotine vaping may harm youth and young adults. Public health bodies tasked with addressing potential public health concerns about nicotine vaping products should consider evidence from this dissertation.

BACKGROUND: Electronic cigarettes (e-cigarettes) are nicotine delivery systems that generate an aerosol that can be inhaled and come in a variety of attractive designs and e- liquid flavorings. E-cigarettes are the second most commonly used tobacco product in the United States and are predominantly used by youth and young adults. The cardiovascular health risk of combustible cigarette use is well-established, but whether e-cigarettes increase the risk of cardiovascular events is less clear. Evaluating the short-term vascular effects of e-cigarette use is an approach to gain insight into the cardiovascular health impact. Limited studies have shown that acute e-cigarette use in combustible cigarette users was associated with increased central hemodynamic values and arterial stiffness. Few studies have assessed the effects of chronic e-cigarette use on arterial stiffness, particularly in young adults. OBJECTIVE: To assess the effects of e-cigarette use on central hemodynamics and arterial stiffness in regular e-cigarette users in comparison to combustible cigarette users and non-users. METHODS: Combustible cigarette users, e-cigarette users, and non-users without known cardiovascular disease (CVD) or CVD risk factors between the ages of 18 and 45 were enrolled in the ongoing Cardiovascular Injury due to Tobacco Products 2.0 (CITU 2.0) study at the Boston University School of Medicine and the University of Louisville School of Medicine starting from 2019. Non-invasive arterial tonometry, using the SphygmoCor system, was performed to measure peripheral artery waveforms to obtain central hemodynamic values and arterial stiffness parameters: augmentation index (AIx), carotid-radial (CR) and carotid-femoral pulse wave velocities (CFPWV). RESULTS: We had available arterial stiffness measures in 209 study participants (mean age 26±7, 48% female) across 3 tobacco product use groups: combustible cigarette users (N=51), e-cigarette users (N=97), and non-users (N=61). Amongst the e-cigarette users, 41 were dual users (use of both e-cigarettes and combustible cigarettes), 25 were exclusive e-cigarette users who were former combustible cigarette users, and 31 were exclusive e-cigarette users who were never combustible cigarette users. The majority (87%) of e-cigarette users used a pod-based product with fruit and mint/wintergreen or menthol as the most popular e-liquid flavors. In unadjusted analyses, central systolic blood pressure, AIx, CRPWV, and CFPWV differed across the three tobacco product use categories. In multivariable regression models adjusting for age, sex, race and study site, e-cigarette users and combustible cigarette users had higher central systolic blood pressure (β=3.9±2.0, p=0.048 and β=4.8±2.4, p=0.04, respectively) whereas combustible cigarette smokers also had higher central AIx, and CRPWV compared to non-users (β=6.9±3.3, p=0.04 and β=0.97±0.31, p=0.002, respectively). In unadjusted analyses across the five groups, we found similar patterns of differences in vascular measures. In multivariable regression models comparing to combustible cigarette users, dual product users had similar measures of vascular function whereas exclusive e-cigarette users who were former smokers had lower CRPWV (β=-0.95±0.36, p=0.009), and exclusive e- cigarette users who were never combustible cigarette users had lower AIx (β=-9.0±4.2, 0.04). CONCLUSIONS: Our findings suggest that in young adults, combustible cigarette use is associated with measures of arterial stiffness. Dual e-cigarette use was largely similar to combustible cigarette use whereas exclusive e-cigarette use had a lesser degree of vascular stiffening. Further studies are needed to evaluate the long-term impact of e- cigarette use on cardiovascular health.

Currently, there is no comprehensive instrument that accounts for all the proposed aspects of vaping dependence simultaneously, nor do current instruments routinely account for factors that may be more unique to vaping dependence. Therefore, the current study addresses these concerns by developing a new multidimensional self-report instrument of vaping dependence. Using guidance from the literature together with expert recommendations, an initial item pool was generated and evaluated. Participants were recruited via Amazon Mechanical Turk, and data was collected via Qualtrics. Data was split into a subsample for exploratory factor analysis (EFA; to determine the latent structure of the proposed instrument) and a subsample for confirmatory factor analysis (CFA; to validate the model structure). EFA suggested a 4-factor model, which was supported by subsequent CFA. These factors were interpreted as: physiological dependence, vaping preoccupation, vaping reinforcement, and loss of control. Data was then reintegrated, and the measure's psychometric properties were evaluated in the overall sample. The total scale and each subscale of the instrument (the Multidimensional Vaping Dependence Index) displayed adequate internal consistency, as well as convergent, discriminant, concurrent, and incremental validity.

Background: Electronic nicotine delivery systems (ENDS) use among adolescents in the United States (U.S.) has surpassed conventional tobacco products (CTPs), including cigarettes. Increasingly, ENDS are used concurrently with CTPs and substances such as cannabis. However, few studies involve Central Appalachia, a region with historically high rates of tobacco and other substance use. Objective: To examine prevalence of concurrent use of ENDS and cannabis among school-going adolescents in Appalachian Tennessee and delineate associations between ENDS use and substance-related risk behavior (cannabis use), social relations (peer use), and school-related risk behavior (academic performance). Methods: Data were obtained from a survey conducted with youth aged 13-17 years in 2018 in a county in Appalachian Tennessee (n = 280). A multivariable logistic regression model was fit to evaluate associations between ENDS and cannabis use, and other factors. Results: Overall, lifetime ENDS and cannabis prevalence estimates were 31.1% and 18.6%, respectively. Lifetime ENDS users had increased odds of also being lifetime cannabis users [OR = 9.22, 95% confidence interval (CI): 3.44-24.75]. Lifetime ENDS users had increased odds of reporting ENDS use among peers [OR = 12.11; 95% CI: 5.40-27.12] and lower academic performance (OR associated with mostly C or D vs. A grades was 4.28, 95% CI: 1.68-10.90). Conclusion: This study found an association between ENDS and cannabis use among adolescents in Appalachian Tennessee exists. Additionally, peer use and academic performance were associated with ENDS use. The findings have implications for public health intervention planning to address not only ENDS but also substance use among Appalachian youth.