Abstract
Introduction:
Researchers have shown a connection between e-cigarette use and subsequent cigarette use. This study prospectively examines the connection between e-cigarette use and marijuana use.
Methods:
This study used data from the Monitoring the Future panel study of 12th graders in 2014 who were followed up 1 year later (n=305). Past 30–day marijuana use and perceived riskiness of marijuana use for 12th graders who used neither e-cigarettes nor cigarettes (78.6%), only e-cigarettes (10.3%), and cigarettes (with or without e-cigarettes; 11.1%) were compared. Data was analyzed in 2019.
Results:
At baseline, 40.1% of e-cigarette-only users, 48.8% of cigarette users, and 13.2% of nonusers reported past 30–day marijuana use at baseline. E-cigarette-only users were less likely to perceive any marijuana as risky at follow-up compared with nonusers (AOR=0.15, 95% CI=0.04, 0.65). Similarly, e-cigarette-only users were more likely to report past 30–day marijuana use at follow-up compared with nonusers (AOR=3.82, 95% CI=1.45, 10.04), as were those who used cigarettes (AOR=7.63, 95% CI=2.65, 21.97).
Conclusions:
E-cigarette use, even when not in conjunction with cigarette use, may be a marker of marijuana use risk during the transition from adolescence to young adulthood. The e-cigarette and marijuana use link may strengthen in the future with the increasing trend of adolescents vaping marijuana.
INTRODUCTION
Prospective studies show adolescent and young adult e-cigarette use is associated with subsequent cigarette use.1,2 E-cigarette use may also be associated with marijuana use risk3; only three studies have assessed this longitudinally.4–6 More generally, research shows a consistent link between tobacco use and subsequent marijuana use.7 Given recent data demonstrating an increase in vaping marijuana among U.S. adolescents and young adults,8,9 this link is important to understand.
Studies suggest that e-cigarette use may influence risk perceptions of other tobacco products.1 Risk perceptions are strongly and inversely associated with behaviors, making them important to understand as precursors to risk behaviors.10–12
Data suggest those who use both e-cigarettes and cigarettes (dual users) differ from e-cigarette-only users and have greater risk for marijuana use compared with e-cigarette-only users.13–15 Risk for marijuana use among e-cigarette-only users has not been prospectively examined in national adolescent samples. This study examined the prospective associations of e-cigarette use and cigarette use in 12th grade with marijuana use and marijuana use risk perceptions concurrently and 1 year later in a national sample of U.S. 12th graders.
METHODS
Study Sample
Data for the study came from the Monitoring the Future panel study, an ongoing study of adolescents and adults in the U.S.16 Approximately 15,000 Grade 12 students are surveyed annually in U.S. schools using a paper and pencil questionnaire. Annually, 2,400 students are randomly selected to be followed longitudinally. Follow-up surveys are conducted 1 year after high school for half of the selected sample and 2 years after high school for the remaining half via mail. Additional data collection details are available elsewhere.9,16 The Monitoring the Future study has been approved by the University of Michigan IRB.
As Monitoring the Future follow-up data are currently available through 2015, the sample for this study used data from the 2014 Grade 12 cohort that was asked about e-cigarette use and successfully followed up in 2015 (n=347; response rate, 42%). Appendix Figure 1 provides details on sample selection. The analysis was limited to those that had complete data on all variables of interest (n=305). Table 1 provides descriptive details for the analytic sample.
Table 1.
Descriptive Statistics (n=305)
| 12th grade characteristics | % |
|---|---|
| Male | 45.8 |
| Race/ethnicity | |
| Black | 14.08 |
| White | 59.47 |
| Hispanic | 16.01 |
| Other | 10.44 |
| Any binge drinking in past 2 weeksa | 18.74 |
| Past 30-day e-cigarette and cigarette use | |
| No use | 78.60 |
| E-cigarette use only | 10.32 |
| Cigarette useb | 11.08 |
| Past 30-day marijuana use | 19.92 |
| Marijuana risk perceptions | |
| Great/moderate risk of any marijuana uses | 29.44 |
| Great/moderate risk of regular marijuana use | 68.82 |
Binge drinking was defined as consuming 5 or more drinks in a row.
This includes both those who used cigarettes and e-cigarettes in the past 30 days and those who only used cigarettes.
Measures
Three categories of use were created based on 12th graders responses to two questions: During the last 30 days, on how many days (if any) have you used electronic cigarettes (e-cigarettes)? and How frequently have you smoked cigarettes in the past 30 days? The categories were: (1) no use, (2) e-cigarette use only, and (3) cigarette use (includes both those who used cigarettes and e-cigarettes and those who only used cigarettes in the past 30 days) in the past 30 days.
Respondents reported on two types of marijuana risk perceptions, any marijuana use risk and regular marijuana use risk, by asking: How much do you think people risk harming themselves (physically or in other ways) if they: […try marijuana once or twice, …smoke marijuana regularly?]. Each was dichotomized from four response options (no risk, slight risk, moderate risk, great risk) into no/slight risk versus moderate/great risk. Marijuana risk perceptions were assessed at 12th grade and at follow-up.
In the 12th grade and follow-up survey, respondents reported on past 30–day marijuana use.
Sex, race/ethnicity (black, white, Hispanic, and other), and past 2–week binge drinking in 12th grade were included as controls. Prospective models also controlled for 12th grade marijuana use or marijuana use risk perceptions.
Statistical Analysis
All analyses incorporated weights to adjust for attrition and oversampling of drug users. First, logistic regression models were estimated to examine cross-sectional associations of e-cigarette and cigarette use in 12th grade with 12th grade marijuana use and marijuana risk perceptions. Models adjusted for sex, race/ethnicity, and binge drinking. Second, logistic regression models estimated the prospective associations of e-cigarette and cigarette use in 12th grade with marijuana use and marijuana use risk perceptions 1 year later. Prospective models controlled for sex, race/ethnicity, binge drinking, and either marijuana use or marijuana risk perceptions in 12th grade, depending on the outcome. All analyses were conducted in 2019 and employed the Stata, version 15.0, svy procedures.
RESULTS
Table 2 provides results for cross-sectional models, controlling for sex, race/ethnicity, and binge drinking. Those who used e-cigarettes only (OR=3.35, 95% CI=1.23, 9.32) and cigarettes (OR=5.00, 95% CI=1.91, 13.08) in the past 30 days were more likely to report marijuana use in the past 30 days. Risk perceptions of any marijuana use did not differ by e-cigarette only and cigarette use.
Table 2.
Cross-sectional and Prospective Associations of E-cigarette and Cigarette Use With Marijuana Use and Marijuana Risk Perceptions
| 12th grade past 30-day e-cigarette and cigarette use | Past 30-day marijuana use | Any marijuana use risk | Regular marijuana use risk |
|---|---|---|---|
| AORa (95% CI) | AORa (95% CI) | AORa (95% CI) | |
| Cross-sectional outcomes at baseline | |||
| No use | ref | ref | ref |
| E-cigarette use only | 3.35 (1.23, 9.32) | 0.66 (0.24, 1.77) | 0.69 (0.29, 1.63) |
| Cigarette useb | 5.00 (1.91, 13.08) | 0.55 (0.18, 1.62) | 0.71 (0.28, 1.80) |
| Prospective outcomes at follow up | |||
| No use | refc | refd | refe |
| E-cigarette use only | 3.82 (1.45, 10.04) | 0.15 (0.04, 0.65) | 0.56 (0.21, 1.45) |
| Cigarette usea | 7.63 (2.65, 21.9.) | 0.12 (0.02, 1.57) | 0.30 (0.12, 0.73) |
Note: Bold indicates significance at p<0.05.
Controls: sex, race/ethnicity, binge drinking in the past 2 weeks.
This includes both those who used cigarettes and e-cigarettes in the past 30 days and those who only used cigarettes.
Controls: sex, race/ethnicity, binge drinking in the past 2 weeks, past 30-day marijuana use in 12th grade.
Controls: sex, race/ethnicity, binge drinking in the past 2 weeks, any marijuana use risk perception in 12th grade (no/slight risk vs moderate/great risk).
Controls: sex, race/ethnicity, binge drinking in the past 2 weeks, regular marijuana use risk (no/slight risk vs. moderate/great risk).
Table 2 provides results from prospective models examining odds of marijuana use and marijuana use risk perceptions 1 year later. Twelfth graders who used e-cigarettes only (AOR=3.82, 95% CI=1.45, 10.04) and used cigarettes (AOR=7.63, 95% CI=2.65, 21.97) in the past 30 days were more likely to report past 30–day marijuana use 1 year later compared with nonusers. Twelfth graders who used e-cigarettes only were less likely to report perceiving any marijuana use as risky 1 year later compared with nonusers (AOR=0.15, 95% CI=0.04, 0.65). Twelfth graders who used cigarettes in the past 30 days were less likely to perceive regular marijuana use as risky (AOR=0.30, 95% CI=0.12, 0.73) compared with nonusers.
As a sensitivity test, the authors separated out those who used cigarettes only and who used cigarettes and e-cigarettes (dual users) in the past 30 days. Dual users had a greater risk of marijuana use (AOR=12.24, 95% CI=3.57, 41.91) and lower odds of perceiving marijuana use as risky (AOR=0.05, 95% CI=0.01, 0.56) compared with nonusers. Owing to the small number of individuals using cigarettes only (n=11), the authors did not have power to reliably estimate outcomes for this group. As an additional sensitivity test, marijuana use risk 1 year later was examined only among individuals who did not report past 30–day marijuana use at baseline. E-cigarette-only users remained more likely to use marijuana (AOR=3.61, 95% CI=1.11, 11.71).
DISCUSSION
This study provides evidence from a nationally representative sample that e-cigarette use, even when not in combination with cigarette use, is associated with future marijuana use risk and lower marijuana risk perceptions. This supports cross-sectional studies that find a positive association of e-cigarette and marijuana use,13–15 and also adds to existing research by showing this association among e-cigarette-only users and demonstrating that this risk remains (controlling for current marijuana use). Given the health and social risks of marijuana use among adolescents and young adults,17 this link is particularly concerning. More research drawing on health behavior theories is needed to understand the role of e-cigarettes in changing risk perceptions and behaviors associated with other substance use.
Limitations
Limitations of this study include the limited sample size particularly of cigarette-only users, the absence of those who dropped out of school before 12th grade, lack of information on what substance(s) individuals vaped, and the reliance on self-report of substance use. However, this study has many strengths including a prospective design of a national sample of 12th graders.
CONCLUSIONS
This study is particularly important in light of the considerable increase in e-cigarette use among adolescents9,18 and the growing concern of health risks associated with vaping marijuana.19 Recent data suggests a large proportion of adolescent marijuana users report vaping as their route of administration.20,21
Supplementary Material
ACKNOWLEDGMENTS
The authors thank Kate Leary and Mahmoud Abdulkarim for editorial assistance.
The content is solely the responsibility of the authors and does not necessarily represent the official views of the sponsors. The development of this manuscript was supported by research grants R01CA203809, R01DA031160, and R01DA044157 from the National Cancer Institute and National Institute on Drug Abuse, NIH.
Footnotes
Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
All authors made significant contributions to this study. The authors declare no conflicts of interest. RJE-P designed the study, undertook the statistical analysis, and wrote the first draft of the manuscript. All authors assisted with data interpretation and manuscript editing.
No financial disclosures were reported by the authors of this paper.
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