The estimated prevalence of high school vaping continues to be high (25.7%) and is consistent with other provincial and national estimates [5]. Approximately 12% of high school students reported vaping exclusively with nicotine vapes and 2.5% reported vaping exclusively with nicotine-free vapes in the past month. Additionally, and in contrast to other research, this study estimated the prevalence of dual-use vaping. Approximately 11.3% of high school students reported the use of both nicotine and nicotine-free vapes in the past month.

This study represents an exploration into sociodemographic and health-related differences between high school students who vape with and without nicotine. While similarities exist between the two types of users, several important differences were noted. In this study, males had higher odds than females of being in each category of past-month vape users. Other research noted similar findings but did not explicitly consider different categories of vaping behavior [23,24]. For example, in a subgroup analysis of university students who were not of legal age (<19 years) to purchase vaping products in Ontario, Canada, Seabrook et al. [7] found that cigarette smoking and cannabis use were the top factors associated with past-month vape use and that 21.8% of underage adolescents had vaped in the past month. The implication of this is that many underage youth are still able to access, and use vapes in Canada. In a large, non-probability school-based sample from Canada, Cole et al. [5] found that the prevalence of youth vaping increased across demographic groups before nicotine-containing vapes became legalized for sale in May 2018 and continued to increase thereafter. However, the study was not able to determine whether students were using vapes containing nicotine. The Canadian Tobacco and Nicotine Survey revealed that, among 15–19 year old Canadians in 2020, the most common reasons for vaping were for enjoyment (27%), just to try it (26%), and to reduce stress (23%) [8]. In a cross-sectional sample of 74,501 Canadian high school students from Alberta, British Columbia, Ontario, and Quebec, 39% of youth in 2018–2019 reported current substance use, 53% were using two or more substances, and vape use (28%) was the most prevalent of all substances and the most common substance combined with binge drinking [12]. Moreover, polysubstance use was more common among males, those with weekly spending money, Indigenous students, those experiencing depression, those having peer support, and those living in Alberta.

In the current study, age was significantly associated with both nicotine and nicotine-free vaping, but in opposite directions. Those in grades 10 and 11 were more likely than grade 9 students to be nicotine vape users, holding other variables constant, while those in grade 9 were more likely to be nicotine-free vape users compared to those in grade 11. For dual-use vaping, those in grade 9 were more likely to use both nicotine and nicotine-free vapes, compared with those in grade 11 or grade 12. Given that patterns of substance use tend to increase with age during adolescence, the nicotine-only results are not that surprising. However, the increased odds of nicotine-free and dual-use vaping among grade 9 students is concerning. Research has found that youth who vape nicotine-free products have a worse understanding of e-cigarette chemicals, compared with those who vape with nicotine [19]. Moreover, this lack of understanding might translate to the unknowing use, and to the subsequent misreporting, of nicotine vaping behavior [19,25]. In a cross-sectional study of four Connecticut high schools and two middle schools, Morean et al. [25] found that 34.1% of adolescents could not quantify the nicotine concentration of the e-liquid in their vapes, and that this was more common among females, nonsmokers, and those who vaped infrequently compared to nicotine users. The higher likelihood of dual-use vaping among grade 9 students in the current study warrants further investigation. Perhaps the behavioral and cultural pressures associated with transitioning to high school account for some of this variation, whereby vape use, in general, signals acceptance and belonging in high school culture. Alternatively, some of the associated mechanisms might be rooted in earlier (e.g., middle school) processes of socialization. Recent research suggests that both proximity and peer/media influence can have a substantial impact on the likelihood of initiating vape use [26,27]. Mantey et al. [26] found that observing vape use at school was associated with greater odds of becoming a user. This is especially concerning considering that they found that two out of three middle and high school students observed their peers vaping at school [26]. In addition to young students being exposed to high levels of vaping at school, Dai et al. [27], found that middle school students tend to be more susceptible to e-cigarette marketing and have lower levels of vaping media literacy, compared to high school students. Peer influence and stress relief were also key motivators for vape use among high school students in Toronto, Ontario [28].

Our findings regarding vaping and other substance use align with other research and add additional context to these associations. Indeed, other research has found that most individuals who smoke also vape [9]. Our findings corroborate this, with a caveat—smokers who vape tend to vape either with nicotine exclusively or with a mix of nicotine and nicotine-free, but rarely do they exclusively vape nicotine-free. These results are not surprising, given that youth see nicotine vape use as a strategy to limit cigarette smoking or to quit [29]. Lifetime alcohol and cannabis use were both associated with past-month vape use, with stronger associations for nicotine-vaping. This is consistent with other Canadian data showing that alcohol, tobacco, and cannabis were associated with a higher risk for vaping in adolescents, as was being employed and having lower grades in school [30]. Given that nicotine is commonly implicated in other patterns of polysubstance use, these results are not surprising [31,32].

Future research should continue to explore risk factors for different types of vape use. While nicotine and nicotine-free use represents one such “type”, other areas of vape use include cannabis and cannabis derivatives (e.g., oil, hash, shatter). Although nicotine vaping is more common than cannabis vaping, [33] one-third of adolescent vape users in Canada use their vaping device to consume cannabis [34]. This is concerning, since those who vape with THC and high-potency cannabis concentrates have a greater risk for psychosis, paranoia, and cannabis hyperemesis syndrome [33]. Thus, it is not surprising that the definition of vaping has expanded recently to include both “e-cigarettes” and the use of a vaporizer for cannabis [35]. Relatedly, vape use should not be regarded as a homogeneous activity and researchers should be explicit in their discussion of what type of vape use was measured. Second, research should focus on the more fundamental causes of vape use, such as the influence of socioeconomic status, gender, and race/ethnicity. This line of thinking is congruent with that proposed by Seabrook and Avison [36], whereby socioeconomic status, cumulative disadvantage processes, and health outcomes are assessed from a life-course perspective. They provided evidence, for example, showing how low socioeconomic status (e.g., living in poverty) is associated with higher risk-taking behavior (e.g., substance use) and greater exposure to and more kinds of stress, which in turn increases the risk of poor health outcomes, amplifying socioeconomic differences in health disparities over time. Consideration of the structural, socioeconomic, and demographic influences of vape use, as well as the development and implementation of surveillance tools that target socioeconomically disadvantaged populations, have also been recently advocated by the Canadian Public Health Association [21]. Similarly, future research should explore more temporal elements of vaping. Exploring patterns and transitions between types of vape use, longitudinally, would illuminate areas most amenable to intervention.

While the current study has several strengths, there are also limitations that need to be considered. Using survey data, the study followed a cross-sectional design, limiting the ability for causal inference [37]. The extent to which vaping behavior precedes, or follows, other health-related behaviors (alcohol use, marijuana use, smoking status) could not be established. Second, measures of vape and other substance use were all based on self-reports. Given the sensitive nature of this behavior, in conjunction with the young age range of the participants, many outcomes were likely underreported. Similarly, the contents of the vapes were self-reported and students may have been unaware of the nicotine content. However, self-reporting using validated instruments is the most common method to capture substance use [1]. Third, we could not establish any temporal sequence to the use of past-month vaping. Therefore, we were unable to differentiate between experimentation and current use or transitions between nicotine and nicotine-free use.