Beyond the Headlines: What Systematic Reviews on Youth Vaping Really Mean

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Key Points:

• Umbrella Review: Tobacco Control study pooled 56 systematic reviews on youth vaping, reporting associations with smoking initiation, substance use, respiratory issues, and mental health.

• Quality Concerns: Nearly 70 percent of reviews rated “critically low” quality; only one met high-quality standards under AMSTAR 2.

• Expert Reactions: Leading scientists warn consistency does not mean causality; most findings stem from observational, cross-sectional data prone to confounding.

• Gateway Questioned: U.S. data show youth and young adult smoking at record lows since e-cig introduction; 18–24 smoking rates fell 82 percent (30.6 percent in 2007 to 5.6 percent in 2023).

• Youth Trends: Cigarette use among high schoolers dropped to 1.1% in 2023; youth vaping has declined since 2019 even as mental health struggles worsened.

• Risk Clustering: Associations with depression, substance use, and suicidal ideation may reflect broader risk-taking behaviors, not direct vaping effects.

• Policy Implications: Reactionary restrictions based on weak evidence could undermine harm reduction for 20 million+ U.S. adult vapers and 30 million+ adult smokers.

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A recent study in Tobacco Control is sounding alarms, yet according to several scientists, the evidence it presents is useful but weak, with significant limitations in proving causality. Questions remain about whether the associations found are due to vaping itself or reflect broader risk-taking behaviors, and population-level evidence often contradicts the idea of a gateway from vaping to smoking.

The study conducted an umbrella review of systematic reviews to examine evidence on short- and long-term effects of e-cigarette use among people under 25. Researchers identified 56 reviews covering 384 unique articles. While most reviews drew heavily on U.S. data, they also included studies from Australia, Belgium, Canada, Finland, Germany, Lebanon, Mexico, the Netherlands, Romania, South Korea, Switzerland, Taiwan, Thailand, and the UK. Importantly, the authors assessed the quality of the reviews they included, which strongly affected the review’s conclusions.

According to the review, 21 systematic reviews consistently found statistically significant associations between e-cigarette use and subsequent smoking initiation, with young people who used e-cigarettes about three times more likely than non-users to begin smoking, based on pooled odds ratios ranging from 1.5 to 26. This pattern suggests a possible causal relationship, though many authors remain cautious. Five systematic reviews found strong associations between e-cigarette use and other substance use, with higher odds of marijuana use, alcohol use, binge drinking, and non-prescribed stimulant use. These findings may indicate clustering of risky behaviors rather than a direct effect of vaping.

Respiratory outcomes were also reported. Seven systematic reviews examined asthma, with pooled odds ratios between 1.20 and 1.36 for diagnosis and 1.44 for exacerbation, although most reviews were rated as critically low quality. Other respiratory issues such as coughing, bronchitis, pneumonia, wheezing, and allergic rhinitis were identified, but evidence was largely based on cross-sectional surveys and case reports, again mostly of critically low quality.

For mental health, the review concluded there were strong associations between vaping and suicidal thoughts, planning, and attempts, as well as higher likelihood of ADHD, depression, eating disorders, and sleep problems. Yet most studies in this area were cross-sectional, making causality unclear.

Policymakers should be wary of the study’s findings. Overall, the review’s quality assessment found that more than two-thirds (69.6 percent) of included reviews were rated “critically low” using the AMSTAR 2 checklist for systematic reviews, with only one review (1.8 percent) rated high quality.

Experts in tobacco control and harm reduction quickly responded.

Professor Ann McNeill of King’s College London cautioned that given the quality ratings, authors should be “extremely cautious before making any conclusions,” adding that “consistency does not mean causality.” She noted her own research found that increases in youth vaping were associated with decreases in smoking.

Dr. Stephen Burgess, statistician at the University of Cambridge, remarked that because the review is a compilation of observational studies, causality cannot be established, and that only randomized trials could provide certainty – though such studies would be impractical and potentially unethical, meaning there may likely never be conclusive evidence.

Professor Peter Hajek of Queen Mary University of London noted that many associations have “well known explanations,” pointing out that young people with mental health issues are more likely to use psychoactive substances in general, which could explain clustering with vaping.

Population data further complicates the gateway narrative.

In the United States, smoking among young adults (ages 18–24) has dropped dramatically since e-cigarettes were introduced in 2007, when 30.6 percent were current smokers. By 2023, smoking in this age group had fallen 81.8 percent to just 5.6 percent, compared to a 39.5 percent decline among all U.S. adults, where 12.1 percent still smoked.

Youth combustible cigarette use is now at record lows: in 2023, only 6.4 percent of high school students reported ever trying a cigarette, and just 1.1 percent reported current use – defined as having used the product on at least one occasion in the 30 days prior.

At the same time, youth e-cigarette use has declined in recent years, while youth mental health challenges have increased. Between 2019 and 2021, ever-use of e-cigarettes among high school students fell by 27.7 percent and current use by 45 percent. During the same period, reports of persistent feelings of sadness or hopelessness rose by 15.3 percent, and suicide attempts increased by 14.6 percent.

Policymakers should therefore be cautious in interpreting the latest review. While monitoring youth use of any age-restricted product is commendable, reactionary policy based on weak or confounded evidence risks doing a disservice to more than 20 million American adults who vaped in 2023 and the over 30 million who smoked. Effective policy must balance vigilance about youth use with ensuring adult access to lower-risk tobacco harm reduction products.

Nothing in this analysis is intended to influence the passage of legislation, and it does not necessarily represent the views of Tobacco Harm Reduction 101.