Abstract
This population epidemiology study uses data from the National Youth Tobacco Survey to assess trends in self-reported use of marijuana in electronic cigarettes among US middle school and high school students from 2017 to 2018.
e-Cigarette use is gaining popularity among US adolescents, and marijuana and other substances besides nicotine can be used in e-cigarettes.1 Since 2012, more states are relaxing the restrictions on marijuana use, and social acceptability of marijuana use is shifting among adolescents.1,2 This study sought to assess self-reported marijuana use in e-cigarettes among US students from 2017 to 2018.
Methods
The National Youth Tobacco Survey (NYTS) is a cross-sectional, school-based survey conducted annually using a stratified, 3-stage cluster sampling design to produce a nationally representative sample of middle school (grades 6-8) and high school (grades 9-12) students in the United States. Participating students completed the survey via pencil and paper. The overall response rates for participating schools and students were 68.1% in 2017 and 68.2% in 2018.3 Students were asked about whether they have ever used marijuana in an e-cigarette. The University of Nebraska institutional review board determined this study to be non–human subjects research.
Weighted estimates and 95% CIs of the prevalence of ever marijuana use in e-cigarettes in 2017 and 2018 were reported using the Taylor series variance estimation. Multivariable logistic regression tested the changes of self-reported ever marijuana use in e-cigarettes between 2017 and 2018, in which year was the predictive variable and covariates included demographics (age, sex, and race/ethnicity) and tobacco use by a household member. Other variables, including ever and current (past 30-day) e-cigarette use, frequency of current e-cigarette use, current cigarette smoking, current other tobacco use, and the number of tobacco products currently used by students, were included in the stratified analysis. Statistical analysis was performed using SAS 9.4 (SAS Institute Inc). P < .05 (2-sided) was used as the threshold for statistical significance.
Results
This pooled sample from the 2017-2018 NYTS (n = 38 061) included 49.1% female, 55.9% high school, 56.5% non-Hispanic white, 13.0% non-Hispanic black, and 24.6% Hispanic students; 23.6% ever e-cigarette users; and 10.9% current e-cigarette users.
From 2017 to 2018, the reported prevalence of ever marijuana use in e-cigarettes among all students increased (11.1% [95% CI, 9.8%-12.5%] vs 14.7% [95% CI, 13.3%-16.1%]; difference, 3.6% [1.6%-5.5%]; P < .001) (Table). The increases were observed across some demographic groups, including male and female students, adolescents aged 13 to 17 years, high school students, and non-Hispanic white and Hispanic students. The largest increases were observed among current users of 1 tobacco product (33.2% to 40.6%; difference, 7.4% [95% CI, 1.8%-13.1%]; P = .02) and those who lived with a household member using e-cigarettes (22.7% to 29.5%; difference, 6.8% [95% CI, 2.2%-11.4%]; P = .007).
Table. Prevalence of Marijuana Use in Electronic Cigarettes Among US Youth, 2017-2018 National Youth Tobacco Survey (N = 38 061).
| Prevalence of Marijuana Use in e-Cigarettes, Weighted % (95% CI)a,b | Change Across Years | |||
|---|---|---|---|---|
| 2017 (n = 17 872) | 2018 (n = 20 189) | 2018 vs 2017, Weighted % (95% CI)a | P Valuec | |
| Overall | 11.1 (9.8 to 12.5) | 14.7 (13.3 to 16.1) | 3.6 (1.6 to 5.5) | <.001 |
| Sex | ||||
| Male | 11.2 (9.8 to 12.5) | 14.6 (13.2 to 16.0) | 3.4 (1.5 to 5.3) | <.001 |
| Female | 10.9 (9.4 to 12.5) | 14.7 (13.0 to 16.4) | 3.8 (1.4 to 6.1) | .007 |
| Age, y | ||||
| 9-12 | 3.0 (2.1 to 3.9) | 2.8 (2.1 to 3.6) | −0.2 (−1.3 to 1.0) | .54 |
| 13-15 | 8.3 (7.2 to 9.5) | 11.1 (9.9 to 12.3) | 2.7 (1.1 to 4.4) | .004 |
| 16-17 | 18.0 (15.8 to 20.1) | 24.1 (21.8 to 26.4) | 6.1 (3.0 to 9.3) | <.001 |
| ≥18 | 23.0 (19.1 to 26.8) | 28.3 (25.3 to 31.4) | 5.4 (0.4 to 10.3) | .09 |
| Grade | ||||
| Middle school | 4.5 (3.7 to 5.2) | 5.5 (4.5 to 6.5) | 1.0 (−0.2 to 2.2) | .15 |
| High school | 16.1 (14.2 to 18.0) | 21.7 (20.1 to 23.3) | 5.6 (3.1 to 8.1) | <.001 |
| Race/ethnicityd | ||||
| Non-Hispanic white | 10.8 (9.2 to 12.3) | 14.5 (12.6 to 16.4) | 3.7 (1.3 to 6.2) | .002 |
| Non-Hispanic black | 10.5 (8.8 to 12.3) | 11.6 (9.3 to 13.8) | 1.1 (−1.8 to 3.9) | .63 |
| Hispanic | 14.1 (12.1 to 16.0) | 18.4 (16.2 to 20.6) | 4.3 (1.5 to 7.2) | .007 |
| Other | 5.5 (3.4 to 7.7) | 8.8 (6.6 to 11.0) | 3.3 (0.2 to 6.4) | .18 |
| Ever users of e-cigarettese | 37.2 (34.0 to 40.4) | 42.7 (40.2 to 45.3) | 5.5 (1.4 to 9.6) | .01 |
| Current use of e-cigarettesf | ||||
| No | 7.4 (6.6 to 8.1) | 8.1 (7.0 to 9.2) | 0.7 (−0.6 to 2.1) | .31 |
| Yes | 51.7 (46.1 to 57.3) | 53.5 (50.2 to 56.8) | 1.8 (−4.7 to 8.3) | .42 |
| No. of days e-cigarettes used in past 30 d, df | ||||
| 1-5 | 43.6 (38.0 to 49.2) | 43.2 (39.2 to 47.2) | −0.3 (−7.2 to 6.6) | .98 |
| 6-19 | 56.3 (47.6 to 65.1) | 56.7 (51.3 to 62.2) | 0.4 (−9.9 to 10.7) | .98 |
| 20-30 | 72.6 (64.3 to 80.8) | 70.9 (66.6 to 75.2) | −1.7 (−11.0 to 7.7) | .63 |
| Current cigarette smokingg | ||||
| No | 8.1 (7.1 to 9.2) | 11.4 (10.1 to 12.7) | 3.3 (1.6 to 4.9) | <.001 |
| Yes | 56.2 (50.3 to 62.1) | 63.4 (59.3 to 67.6) | 7.2 (0.0 to 14.4) | .11 |
| Current use of other tobacco productsh | ||||
| No | 7.3 (6.3 to 8.3) | 10.4 (9.2 to 11.6) | 3.1 (1.5 to 4.7) | <.001 |
| Yes | 53.3 (48.9 to 57.7) | 56.6 (52.8 to 60.4) | 3.3 (−2.5 to 9.1) | .33 |
| No. of tobacco products currently usedh | ||||
| 0 | 5.5 (4.8 to 6.2) | 6.4 (5.6 to 7.3) | 1.0 (−0.2 to 2.1) | .10 |
| 1 (single use) | 33.2 (29.1 to 37.2) | 40.6 (36.6 to 44.5) | 7.4 (1.8 to 13.1) | .02 |
| 2 (dual use) | 56.5 (49.8 to 63.2) | 57.1 (51.8 to 62.5) | 0.6 (−8.0 to 9.2) | .87 |
| ≥3 (poly use) | 65.8 (60.1 to 71.5) | 71.6 (67.7 to 75.4) | 5.8 (−1.1 to 12.6) | .04 |
| Tobacco use by household membersi | ||||
| None | 7.6 (6.3 to 8.9) | 10.5 (9.0 to 12.0) | 2.9 (1.0 to 4.9) | .003 |
| e-Cigarettes | 22.7 (18.8 to 26.6) | 29.5 (27.1 to 32.0) | 6.8 (2.2 to 11.4) | .007 |
| Other tobacco products | 15.2 (13.5 to 17.0) | 17.8 (15.7 to 19.9) | 2.5 (−0.2 to 5.3) | .04 |
Weighted estimates and 95% CIs were reported by taking the complex survey design (sampling weight, stratum, and cluster) into account using the Taylor series variance estimation.
In the 2017 and 2018 National Youth Tobacco Surveys, marijuana use in e-cigarettes was assessed by the response yes to the question “Have you ever used marijuana, marijuana concentrates, marijuana waxes, THC, or hash oils in an e-cigarette?”
Multivariable logistic regression was performed, in which ever marijuana use in e-cigarettes (yes vs no) was the outcome variable, year (2017-2018, categorical) was the predictive variable, and covariates included age, sex, race/ethnicity, and tobacco use by a household member.
Race and Hispanic ethnicity were self-reported, and Hispanic persons could be of any race.
Ever e-cigarette use was assessed by the question “Have you ever used an e-cigarette, even once or twice?”
Current e-cigarette use and No. of days e-cigarettes used were assessed by the question “During the past 30 days, on how many days did you use e-cigarettes?”
Defined as students who reported smoking cigarettes 1 or more days in the past 30 days.
Defined as students who reported use of cigars, little cigars, or cigarillos; pipes filled with tobacco; bidis; hookah or waterpipe; smokeless tobacco (ie, chewing tobacco, snuff or dip, snus, dissolvable tobacco products) 1 or more days in the past 30 days for any listed product.
Defined by the question “Does anyone who lives with you now…? (Select one or more).”
In 2018, 42.7% (95% CI, 40.2%-45.3%) of ever e-cigarette users, 53.5% (95% CI, 50.2%-56.8%) of current e-cigarette users, and 71.6% (95% CI, 67.7%-75.4%) of poly tobacco users reported ever using marijuana in e-cigarettes.
Discussion
This study identified a significant increase in self-reported ever marijuana use in e-cigarettes from 2017 to 2018 among US students, using the most current data available at the national level. Prevalence estimates reported for all students (14.7%) and current e-cigarette users (53.5%) in 2018 were also much higher than those reported in 2016 (8.9% and 39.5%, respectively),2 although changes in the wording and placement of survey questions about marijuana use in e-cigarettes after 2016 may limit direct comparisons.
The increase in marijuana use in e-cigarettes could be attributable to the increase of sales of pod-mod–style e-cigarette products, access to marijuana through informal sources (eg, friends, family members, illicit dealers),4,5 and reduced perception among adolescents of the harms of marijuana use.1
Marijuana use in adolescence could lead to adverse effects on brain development, mental health, and academic performance.6 e-Cigarette use has also been related to severe respiratory diseases, with 2290 vaping-related lung injury cases reported and 47 deaths confirmed as of November 20, 20194; approximately 77% of cases were in people with a history of vaping tetrahydrocannabinol-containing products.5 Longitudinal studies are needed to assess the acute and long-term health effects of vaping marijuana in e-cigarettes.
Study limitations are that self-reported information is subject to recall and social desirability biases. Continuous surveillance of youth vaping of marijuana is warranted.
Section Editor: Jody W. Zylke, MD, Deputy Editor.
References
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