Initiation Patterns and Trends of E-Cigarette and Cigarette Use Among U.S. Adolescents

Products and patterns through which adolescents, young adults, and adults initiate co-use of tobacco and cannabis

BACKGROUND

Co-use of tobacco and cannabis is common. However, few studies have examined the temporal sequencing through which individuals initiate co-use, and how these patterns vary across age. This study addresses this gap by examining the specific products and temporal sequencing through which adolescents, young adults, and adults initiate co-use of tobacco and cannabis. Among adolescents, young adults, and adults who co-used tobacco and cannabis in the past 30 days, we examined (a) whether tobacco or cannabis was used first in their lifetime and (b) which specific tobacco or cannabis product (e.g., nicotine e-cigarettes, cannabis edibles) was the first used.

METHODS

Data were from a cross-sectional national survey (N = 6,131, 13-40 years old) in which participants reported ever use, past-30-day-use, and order of use for 17 different tobacco and cannabis products. Results were analyzed overall and by age group (13-20; 21-24; 25-40).

RESULTS

38.4% of participants reported use of both tobacco and cannabis in the past 30 days. Among these participants, 70.9% used tobacco first in their lifetime (66.6% < 21; 71.7% 21-24; 76.6% > 24). Approximately 60% of participants who initiated co-use with tobacco reported nicotine e-cigarettes as their first tobacco product (63.3% < 21; 66.7% 21-24; 49.6% > 24).

CONCLUSIONS

The majority of participants who used both tobacco and cannabis used tobacco first in their lifetime, and nicotine e-cigarettes were the most common form of tobacco initiation, particularly among adolescents and young adults. Findings emphasize the need for co-use prevention programs to target common products of initiation.

Trends of Single, Dual, and Polytobacco Use Among School-Based Students in the United States: An Analysis of the National Youth Tobacco Survey

PURPOSE

To examine trends in single, dual, and polytobacco use between 2014-2020 for US youth and to identify disparities in these trends by grade level, sex, and race/ethnicity.

DESIGN

A secondary analysis of the National Youth Tobacco Survey (NYTS).

SUBJECTS

A total of 122 566 students.

MEASURES

Past 30-day exclusive use of cigarettes, e-cigarettes, other combustibles (cigars, little cigars, cigarillos, hookah, pipe tobacco, bidis) and smokeless tobacco (snus, smokeless, dissolvable); dual use of each product with e-cigarettes; polyuse with e-cigarettes; dual/polyuse without e-cigarettes.

ANALYSIS

Multivariable modified Poisson regression.

RESULTS

Compared to 2014, exclusive e-cigarette use (APR = 2.51, 95% CI: 1.96, 3.21) trended upward while exclusive cigarette (APR = .34, 95% CI: .23, .50), 'other' combustibles (APR = .47, 95% CI: .37, .58), and smokeless tobacco (APR = .40, 95% CI: .25, .65) use trended downward in 2020. Polytobacco use with and without e-cigarettes trended downward in 2020 compared to 2014. We also saw differences in trends across sociodemographic groups. Comparing 2020 to 2014, exclusive e-cigarette use was higher for females than males, 'other' combustible tobacco use remained stable for Non-Hispanic Black students but decreased for other racial/ethnic groups, and dual e-cigarette/cigarette use trended upward more for middle school students than high school students.

CONCLUSIONS

Despite decreased trends in tobacco product use without e-cigarettes between 2014-2020, differences in tobacco product use trends by grade level, sex, and race/ethnicity were identified. Prevention efforts targeting disparities in tobacco product use are needed.

Systematic Review and Critical Analysis of Longitudinal Studies Assessing Effect of E-Cigarettes on Cigarette Initiation among Adolescent Never-Smokers

Prospective longitudinal studies mainly conclude on a causal role of e-cigarettes in the initiation of cigarettes in flagrant contradiction with conclusions drawn from epidemiology and other studies showing a sharp decline in cigarette use in parallel with the spread of e-cigarette use. This systematic review explores the reasons for this discrepancy.

METHODS

Among 84 publications on e-cigarette/cigarette association in adolescents identified in the Medline database from 2011 to 2022, 23 concern 22 never-smoker longitudinal sub-cohorts.

RESULTS

A link between e-cigarette experimentation at T1 and cigarette initiation at T2 is reported in sub-cohort analyses of never-smokers (AOR: 1.41 to 8.30). However, studies exclude 64.3% of T1 e-cigarette experimenters (because of dual-use) and 74.1% of T2 cigarette experimenters. With this study design, e-cigarettes contribute only to 5.3% of T2 cigarette experimentation, casting major doubt on the external validity of results and authors' conclusions that e-cigarettes have a significant effect on the initiation of cigarettes (Gateway effect) at the population level. This sub-cohort design prohibits highlighting any Diversion effect, which is the most likely mechanism accounting for the competition between these two products.

CONCLUSIONS

While nicotine abstinence remains the best medical option, over-regulation of e-cigarettes because of misinterpretation of longitudinal study results may be detrimental to public health and tobacco control.

Latin America and the Caribbean Code Against Cancer 1st edition: Tobacco and nicotine-related products, secondhand smoke, and alcohol and cancer

Tobacco, secondhand smoke (SHS), and alcohol, all carcinogens, are leading preventable cancer risk factors in Latin America and the Caribbean (LAC). Since 2000, smoking and SHS exposure have significantly decreased in the region. Yet alcohol consumption remains high. The entry of nicotine-related products such as electronic cigarettes (e-cigs) threatens achievements made in tobacco control and chronic diseases prevention, including cancer. E-cigs use is likely associated with smoking initiation among adolescents who had never smoked and dual use with combustible tobacco products. Therefore, the LAC Code Against Cancer recommends to the public actions they can take to reduce their risk of cancer: 1. Don't smoke or use any type of tobacco. If you do, quitting is possible, with professional help if needed. Don't use e-cigarettes either, as they lead to tobacco use. 2. Make your home a smoke-free place. Respect and promote laws that ensure smoke-free spaces to protect our health. and 3. Avoid drinking alcoholic beverages. This helps prevent several types of cancer. The Code recommends to policymakers a package of cost-effective policies based on the MPOWER and SAFER to prevent cancer at the population level. It also recommends that primary care health professionals: 1. Ask all their patients and their families whether they smoke or vape, inform them about the harms of smoking and vaping, and promote tobacco and nicotine related products cessation strategies among users. 2. Inform about the harms of exposure to SHS, especially among children, and promote smoke-free environments, and 3. Prevent alcohol use by their patients and their families, use tools to assess use, intensity, and frequency, and apply brief counseling intervention to support alcohol abstinence in primary care.

Evaluating a Multicomponent e-Cigarette Prevention Program in the Rural Northwest: Teacher and Parent/Guardian Program Outcomes

There are effective prevention strategies to combat increasing rates of youth e-cigarette use. This study assessed the outcomes of an e-cigarette prevention program with teachers and parents/guardians across a three-county rural area. Researchers assessed teachers' and parent/guardians' increased knowledge and confidence in implementing vape prevention after receiving evidence-based trainings. Pre- and post-surveys demonstrated that teachers had a statistically significant increase in knowledge gain across all eight vape-specific domains assessed as expected. The parent/guardian pre- and post-survey results also show that knowledge and confidence increased significantly across seven domains. Findings suggest that multicomponent e-cigarette education and prevention programs better prepare teachers and parents/guardians to intervene with youth e-cigarette use and initiation, including being more likely to talk to youth about the risks of tobacco and vaping. Recommendations for school nurses are discussed and include educating youth, families, and staff for positive impacts.

Nicotine Addiction and Intensity of e-Cigarette Use by Adolescents in the US, 2014 to 2021

IMPORTANCE

As e-cigarettes have become more effective at delivering the addictive drug nicotine, they have become the dominant form of tobacco use by US adolescents.

OBJECTIVE

To measure intensity of use of e-cigarettes, cigarettes, and other tobacco products among US adolescents and their dependence level over time.

DESIGN, SETTING, AND PARTICIPANTS

This survey study analyzed the cross-sectional National Youth Tobacco Surveys from 2014 to 2021. Confirmatory analysis was conducted using Youth Behavioral Risk Factor Surveillance System from 2015 to 2019. The surveys were administered to national probability samples of US students in grades 6 to 12.

EXPOSURES

Use of e-cigarettes and other tobacco products before and after the introduction of e-cigarettes delivering high levels of nicotine.

MAIN OUTCOMES AND MEASURES

First tobacco product used, age at initiation of use, intensity of use (days per month), and nicotine addiction (measured as time after waking to first use of any tobacco product).

RESULTS

A total of 151 573 respondents were included in the analysis (51.1% male and 48.9% female; mean [SEM] age, 14.57 [0.03] years). Prevalence of e-cigarette use peaked in 2019 and then declined. Between 2014 and 2021, the age at initiation of e-cigarette use decreased, and intensity of use and addiction increased. By 2017, e-cigarettes became the most common first product used (77.0%). Age at initiation of use did not change for cigarettes or other tobacco products, and changes in intensity of use were minimal. By 2019, more e-cigarette users were using their first tobacco product within 5 minutes of waking than for cigarettes and all other products combined. Median e-cigarette use also increased from 3 to 5 d/mo in 2014 to 2018 to 6 to 9 d/mo in 2019 to 2020 and 10 to 19 d/mo in 2021.

CONCLUSIONS AND RELEVANCE

The changes detected in this survey study may reflect the higher levels of nicotine delivery and addiction liability of modern e-cigarettes that use protonated nicotine to make nicotine easier to inhale. The increasing intensity of use of modern e-cigarettes highlights the clinical need to address youth addiction to these new high-nicotine products over the course of many clinical encounters. In addition, stronger regulation, including comprehensive bans on the sale of flavored tobacco products, should be implemented.

Harm perceptions, JUUL dependence, and other tobacco product use among young adults who use JUUL

INTRODUCTION

The study identified groups of JUUL using young adults based on their use patterns and compared harm perceptions, JUUL dependence, and other tobacco product use among these groups.

METHODS

Online cross-sectional survey data were gathered in March 2019 from 667 undergraduate students who used JUUL weekly (50.4% females, average age: 20.3 years) at a southwest U.S. university.

RESULTS

Latent class analysis identified four groups of young adults who used JUUL: 1) Light Social JUUL Using Young Adults (LS, 52.5%) who used JUUL occasionally with friends when drinking alcohol, 2) Daily Sensation Seekers (DSS, 16.2%) who used JUUL daily with alcohol, 3) Daily Activity Driven JUUL Using Young Adults (DAD, 26.0%) who used JUUL daily while drinking, watching media, or studying, and 4) Daily All Occasion JUUL Using Young Adults (DAO, 5.3%) who used JUUL heavily, daily and in various occasions. While all four groups reported some extent of JUUL dependence, DAO reported the highest dependence and were more likely than LS to have used cigarettes and other e-cigarettes besides JUUL. They also tended to believe different pod flavors could cause different types of lung damage while the other groups were unsure/disagreed with this belief. LS were more likely than DSS and DAD to believe that JUUL use indicated openness to new experiences.

CONCLUSION

Young adults with different JUUL use patterns perceived JUUL harms differently and faced varied risks of JUUL dependence and other tobacco product use. Effective cessation interventions should be adapted to meet the needs of these groups.

Sociodemographic Patterns of Exclusive and Dual Combustible Tobacco and E-Cigarette Use among US Adolescents-A Nationally Representative Study (2017-2020)

This study assessed the sociodemographic predictors of exclusive and dual use of the most frequently used nicotine/tobacco products, e-cigarettes, and combustible tobacco among adolescents. Cross-sectional data was from the 2017-2020 Monitoring the Future nationally representative study of eighth, tenth, and twelfth-grade students. We coded past 30 day nicotine/tobacco use into four mutually exclusive categories: no use, e-cigarette use only, combustible use (cigarette or cigar) only, and dual use (e-cigarette and combustible). We pooled the 2017-2020 data to examine the relationship between sex, race/ethnicity, parental education, and each product-use category using multinomial logistic regression, stratified by grade level. Among eighth (N = 11,189), tenth (N = 12,882), and twelfth graders (N = 11,385), exclusive e-cigarette use was the most prevalent pattern (6.4%, 13.2%, 13.8%, respectively), followed by dual use (2.7%, 4.5%, 8.9%), and exclusive combustible use (1.5%, 2.5%, 5.3%). eighth and tenth-grade adolescents whose highest parental education was a 4-year college degree or more had lower odds of exclusive combustible and dual use when compared to adolescents whose highest parental education was less than a high school degree. Research should continue to monitor the differential use of combustible tobacco products and e-cigarettes among adolescents from low socioeconomic status backgrounds or racial/ethnic minority households to inform ongoing and future interventions or policies.

Association between school-based tobacco retailer exposures and young adolescent cigarette, cigar and e-cigarette use

BACKGROUND

Associations between retail tobacco availability and tobacco use have been mixed. This study examined associations between school-based retail environment exposures and current use of cigarettes, cigar products and e-cigarettes among middle school youth in Cleveland, OH.

METHODS

Retailers selling tobacco products were identified using the 2015 Cleveland Food Retail Database (n=639 stores). Youth survey data were drawn from the 2016 Cleveland Youth Risk Behavior Survey, administered to all 7th/8th graders across the Cleveland Metropolitan School District (n=3778, response rate=83.0%). Past 30-day cigarette, cigar product and e-cigarette use were assessed. Student demographics, number of days walking to/from school each week and number of times youth stopped at a retailer to/from school each week were included. For each school (n=63), tobacco retail density (TRD) and proximity (TRP) to nearest retailer were calculated for each product. Multiple regression analysis assessed associations between retail exposures and youth tobacco use.

RESULTS

Across all schools, 3.9%, 10.2% and 8.6% of students currently use cigarettes, cigar products and e-cigarettes, respectively, and 15.2% currently use at least one tobacco product. TRD and TRP were not associated with current use; frequency of walking to school and stopping at retailers were strongly associated with current use.

CONCLUSIONS

Although TRD and TRP were not significantly associated with tobacco product use, youth who reported regularly walking to/from school or who reported stopping at a retail store before/after school were significantly more likely to be a current tobacco product user. This may be due to increased exposure to exterior and point-of-sale marketing.

Use of electronic nicotine delivery systems (ENDS) among U.S. women of reproductive age: Prevalence, reported reasons for use, and toxin exposure

Given the rapidly expanding marketplace for Electronic Nicotine Delivery Systems (ENDS), it is important to monitor patterns of use, particularly among vulnerable populations. This study examined ENDS prevalence, reasons for use (i.e., to help quit smoking and for appealing flavors), and toxin exposure among U.S. women of reproductive age using data from the Population Assessment of Tobacco and Health (PATH) Study (2013-17). Exclusive ENDS users, dual users of ENDS and cigarettes, and exclusive cigarette smokers were compared within and between pregnant and not-pregnant women. Among pregnant women, prevalence of exclusive ENDS and dual use was similar (0.8%; 95%CI = 0.4-1.2% vs. 1.4%; 95%CI = 0.9-2.0%, respectively), but exclusive ENDS use was less prevalent than dual use among not-pregnant women (1.1%; 95%CI = 0.9-1.4% vs. 3.7%; 95%CI = 3.3-4.0%, respectively). Most women reported ENDs were used to help quit smoking (66.5-90.0%) and for appealing flavors (57.6-87.4%), and endorsement rates did not differ by use pattern or pregnancy status. Except for metals, toxin exposure was substantially lower for exclusive ENDS users relative to dual users and exclusive cigarette smokers regardless of pregnancy status. Pregnant and not-pregnant U.S. women regularly report using ENDS for help with quitting smoking and for appealing flavors. Although no type or pattern of tobacco/nicotine use is safe, especially during pregnancy, using ENDS exclusively is consistent with lower overall toxin exposure for pregnant and not-pregnant women. This study advances understanding of ENDS use and toxin exposure in women of reproductive age, a population highly vulnerable to the effects of nicotine/tobacco consumption.

E-cigarette vape and lung ACE2 expression: Implications for coronavirus vulnerability

Evidence in humans suggests a correlation between nicotine smoking and severe respiratory symptoms with COVID-19 infection. In lung tissue, angiotensin-converting enzyme 2 (ACE2) appears to mechanistically underlie viral entry. Here, we investigated whether e-cigarette vapor inhalation alters ACE2 and nicotinic acetylcholine receptor (nAChR) expression in male and female mice. In male lung, nicotine vapor inhalation induced a significant increase in ACE2 mRNA and protein, but surprisingly, these differences were not found in females. Further, both vehicle and nicotine vapor inhalation downregulated α5 nAChR subunits in both sexes, while differences were not found in α7 nAChR subunit expression. Finally, blood ACE2 levels did not differ with exposure, indicating that blood sampling is not a sufficient indicator of lung ACE2 changes. Together, these data indicate a direct link between e-cigarette vaping and increased ACE2 expression in male lung tissue, which thereby reveals an underlying mechanism of increased vulnerability to coronavirus infection in individuals vaping nicotine.

Variation in Health Among Unstably Housed Youth From Cities, Suburbs, Towns, and Rural Areas

PURPOSE

Youth face similar rates of homelessness across rural and urban areas, yet little is known about how the health of unstably housed youth varies by location. We assessed differences in health by location (city, suburb, town, and rural) and housing status among youth facing a range of unstable housing experiences.

METHODS

This secondary data analysis from 8th, 9th, and 11th graders completing the 2019 Minnesota Student Survey examined youth who had experienced housing instability in the prior year (n = 10,757), including running away (48%) or experiencing homelessness (staying in shelter, couch-surfing, or rough sleeping) with (42%) or without (10%) an adult family member. We conducted multifactor analysis of variance to assess differences by location (urban, suburban, town, and rural) and housing experience for each of five health indicators: suboptimal health, depressive symptoms, suicide attempts, ≥2 sexual partners, and e-cigarette use.

RESULTS

In main effects models, all health indicators varied based on housing status; suboptimal health, ≥2 sexual partners, and e-cigarette use also varied by location. Interaction models showed that unaccompanied homeless youth in suburbs reported poorer health compared with those in cities. Compared with suburbs, youth in towns were more likely to report ≥2 sexual partners (19.9%, 24.1%) and e-cigarette use (39.5%, 43.3%).

CONCLUSIONS

Our findings suggest that unstably housed youth face a similar burden of poor health across locations, with only subtle differences in health indicators, yet most research focuses on urban youth. Future research is needed to identify how to best meet the health needs of unstably housed youth across locations.

The Association Between Risk Behaviors and Vaping Among Youth in New Mexico

CONTEXT

Electronic-cigarette use, or vaping, among youth has increased substantially in recent years. Tobacco smoking shows a strong association with other risk behaviors, but the association between vaping and other risk behaviors has rarely been explored. We examine the relationship between youth vaping and substance use, risky driving behaviors, and lack of bicycle helmet use.

PROGRAM

Data from the 2015 and 2017 New Mexico Youth Risk and Resiliency Survey were analyzed to evaluate the association between the use of e-cigarettes and other youth risk behaviors. Study participants were high school students, grades 9 to 12. Logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals (CI).

EVALUATION

A majority of students reported ever using e-cigarettes (54%). In 2015, e-cigarette users were more likely than nonusers to be Hispanic (65% vs 54%, P ≤ .001) and 16 years of age or older (58% vs 42%, P = .018). We found strong, statistically significant associations between e-cigarette use and not wearing a bicycle helmet (OR = 2.62, 95% CI: 1.95-3.51), texting while driving (OR = 2.18, 95% CI: 1.79-2.66), driving after drinking (OR = 2.95, 95% CI: 1.61-5.40), current marijuana use (OR = 6.38, 95% CI: 4.65-8.76), current painkiller use (OR = 2.47, 95% CI: 1.63-3.77), and current heroin use (OR = 0.15, 95% CI: 0.06-0.33). Driving after drinking was not significantly associated with e-cigarette use in 2017.

DISCUSSION

E-cigarette use is associated with multiple other risk behaviors among youth. Further research should focus on environmental and policy efforts to reduce access to e-cigarettes by youth as well as interventions that address the underlying causes of the constellation of risk behaviors.

Alcohol, cigarette, e-cigarette and marijuana use among adolescents and young adults with chronic kidney disease in North America

PURPOSE

This study aimed to describe substance use (SU) among adolescents and young adults (AYA) with chronic kidney disease, compare these findings with the general population, and identify associated risk factors.

METHODS

708 AYA participants contributing 2475 person-visits from the Chronic Kidney Disease in Children Study were used to estimate prevalence rates of past year and 30-day alcohol, cigarette, e-cigarette and marijuana use, and were compared with national surveys. Repeated measures logistic regression estimated the association between SU and participant characteristics.

RESULTS

There was nearly no SU among those 12 to 14 years, but use increased with age, and past year alcohol use was about 80% for those greater than or equal to 22 years. Rates of use among males were constant or increased with age, while rates of use among females were lower after age 22 compared to ages 18 to 22. Associated risk factors included non-Black and non-Hispanic identity, older age, and worse disease severity. Participants were less likely to use substances compared to the general population, especially those 14-18 years.

CONCLUSIONS

SU was less common in AYA with chronic kidney disease than the general population, but differences were attenuated among those greater than or equal to 18 years. Ages 12-14 appear to be the ideal time for prevention efforts. As the landscape of e-cigarette and marijuana policies change, these results underscore the need to understand how similar high-risk populations engage in SU.

Past 30-Day Marijuana Vaping: Prevalence and Predictors of Use in a Nationally Representative Study of U.S. Youth

INTRODUCTION

Vaping has become an increasingly common mode of administration for marijuana among youth, but there are limited data on its prevalence. There is a need to better understand youth prevalence of past 30-day marijuana vaping and its predictors.

METHODS

Data were from a nationally representative sample of students from the Monitoring the Future survey in 2018 (N=9,131). This study examined past 30-day prevalence of marijuana vaping, and for a subset with complete data (n=5,755), the predictors of marijuana vaping among respondents asked about that behavior. Bivariate chi-square tests and multivariable logistic regression estimated the extent to which various factors were associated with marijuana vaping. These factors included the current use of various substances, school-related risk behaviors, attitude and risk behaviors related to substance use, and selected sociodemographic variables.

RESULTS

Past 30-day prevalence of marijuana vaping was higher among 10th graders, male youth, and those in the Other race/ethnicity category. Students who engaged in current past 30-day alcohol use, cigarette use, binge drinking, and nonmedical use of prescription drugs had significantly greater odds of past 30-day marijuana vaping. Past 30-day use was more common among students with a lower perceived risk of marijuana use, those who claimed that it was easy to obtain a vaporizer or marijuana, students with a lower grade point average, and those with recent truancy.

CONCLUSIONS

Past 30-day marijuana vaping is prevalent among U.S. students, and there are robust associations between use and school- and substance-related risk behaviors. These results suggest that the emergence of vaping products might redefine populations at risk, which should be taken into account by marijuana regulatory policies or prevention programs.

E-cigarette use and cigarette smoking initiation among Australian women who have never smoked

INTRODUCTION AND AIM

Evidence regarding the association between e-cigarette use and subsequent initiation of smoking mostly relates to the US population. In Australia, no studies are available investigating the association between the uses of e-cigarettes and smoking initiation among young adults who have never smoked. This study aimed to determine the association between lifetime e-cigarette use and subsequent initiation of cigarette smoking among tobacco-naïve Australian women aged 20-27.

DESIGN AND METHODS

The current study used data (n = 5398) from the third (2015) and fourth (2016) surveys collected from a cohort of Australian women born in 1989-1995 who participated in the Australian Longitudinal Study on Women's Health. Multivariable logistic regression was used to identify the association between lifetime e-cigarette use at the baseline survey and initiation of cigarette smoking (smoked 100 cigarettes or more in the last year) at the follow up adjusting for possible confounders. Effects were expressed as odds ratios with 95% confidence interval.

RESULTS

The mean (± SD) age of the study participants at baseline (third survey) was 22.5 (±1.7). Ever e-cigarette use at baseline was positively associated with smoking initiation at follow up (adjusted odds ratio 3.71; 95% confidence interval 2.33, 5.93). History of depression, binge drinking and higher childhood adversity score were also risk factors for subsequent smoking initiation in the follow up.

DISCUSSION AND CONCLUSIONS

This study identified a strong association between e-cigarette use and subsequent initiation of smoking. Enforcing the existing restriction of sale and supply of e-liquid containing nicotine is essential to prevent never smokers from nicotine addiction via e-cigarettes.

Changes in the Order of Cigarette and Marijuana Initiation and Associations with Cigarette Use, Nicotine Vaping, and Marijuana Use: U.S. 12th Grade Students, 2000-2019

This study (a) examined changes in marijuana and cigarette initiation sequencing and (b) considered implications of such changes for prevention efforts by examining associations between initiation sequencing and current adolescent substance use. Analyses used 2000-2019 cross-sectional data from the national Monitoring the Future (MTF) study (78,252 U.S. 12th grade students). Models examined trends in six distinct patterns of initiation order, and multivariable associations between order of initiation and 30-day cigarette and marijuana use prevalence, cigarette and marijuana use frequency among users, and nicotine and marijuana vaping prevalence. While the percentage of students initiating neither cigarettes nor marijuana increased, increases also were observed in marijuana-only initiation (the fastest-growing pattern) and initiation of marijuana before cigarettes; these increases were accompanied by a significant decrease in cigarette-only initiation. Cigarette use prevalence and frequency were highest among students initiating cigarettes before marijuana; marijuana use prevalence and frequency were highest among students initiating marijuana before cigarettes. Cigarette and marijuana prevalence, as well as marijuana frequency, were lowest among students initiating only a single substance. Nicotine vaping was less prevalent among students initiating a single substance versus both substances, but no significant differences were observed in nicotine vaping prevalence between those initiating only cigarettes versus only marijuana. Implications of these findings for prevention efforts are discussed in the frameworks of both the common liability model and route of administration model.

Trends in E-Cigarette, Cigarette, Cigar, and Smokeless Tobacco Use Among US Adolescent Cohorts, 2014-2018

Objectives. To examine changes in age of initiation of e-cigarette, cigarette, cigar, and smokeless tobacco use among adolescents in the United States.Methods. We used data from 5 cohorts of the National Youth Tobacco Survey (2014-2018; n = 26 662).Results. In 2014, 8.8% of lifetime e-cigarette users initiated use at 14 years or younger, as compared with 28.6% of lifetime e-cigarette users in 2018. There was no such change in initiation ages for cigarettes, cigars, and smokeless tobacco among lifetime users of each of these products.Conclusions. US adolescents are initiating e-cigarette use at younger ages in recent years. This is concerning given the association of e-cigarette use with subsequent cigarette use. Continued surveillance of these trends and additional prospective research are needed. Tobacco prevention programs, policies, and regulations that make it more difficult for youths to obtain e-cigarettes are warranted.