Is vaping the gateway to smoking?

By Dr. Liji Thomas, MDReviewed by Lily Ramsey, LLMFeb 13 2025

Systematic review finds weak evidence for e-cigarettes as a gateway to smoking, highlighting the need for more robust research to guide policy decisions.

Study: Electronic cigarettes and subsequent cigarette smoking in young people: A systematic review. Image Credit: Alena Lom/Shutterstock.com

Electronic cigarettes (e-cigarettes or vapes) entered the market in 2004, introduced by a Chinese company. With their variety of flavors and the promise of avoiding the harmful toxins produced by tobacco combustion, they quickly gained popularity, particularly among young people.

A recent study published in Addiction reviews the available evidence on the link between vaping and subsequent smoking among individuals under 29.

Introduction

Smoking is responsible for over eight million deaths annually worldwide. E-cigarettes, designed to mimic traditional cigarettes, use a vaporizer to produce an inhalable aerosol from a nicotine-containing e-liquid, which also includes various additives.

Regulations surrounding vaping remain inconsistent, differing across regions and countries in both strictness and legal age restrictions.

There is ongoing debate about whether vaping encourages later smoking, either by leading non-smokers to start or by pushing occasional smokers toward regular use. Understanding this relationship is crucial for shaping effective regulatory policies.

About the study

This systematic review aimed to assess how the use and availability of e-cigarettes influence smoking rates at the population level. Researchers also examined secondary outcomes, including smoking initiation, progression, and cessation, comparing e-cigarette users with non-users in individual surveys.

The review analyzed 126 studies, including 27 population-level studies 16 of which had a serious risk of bias.

Of the remaining 99 individual-level studies, 40 (classified as Tier 1) included 5,000 or more participants, yet all carried a serious risk of bias. Many of the studies were conducted in the United States.

Study findings

The review found no strong evidence that vaping reduces smoking rates among young people. The available studies were heavily affected by bias, and their findings were often conflicting.

Overall, increased vape availability correlated with higher vaping rates but lower-than-expected subsequent smoking rates among young people. The data did not strongly support the idea that vaping serves as a gateway to smoking initiation.

However, these conclusions are limited by the quality of the included studies. Among the 12 studies suggesting reduced smoking rates and the two studies indicating higher smoking rates due to vaping, all had serious or critical risk of bias. Only two studies linked e-cigarette use to lower subsequent smoking rates, both of which were also seriously biased.

The evidence for a causal relationship between vaping and smoking initiation, progression, or cessation was similarly weak. Individuals who used vapes at the start of a study were consistently more likely to begin smoking or increase their smoking over time.

This observation needs further confirmation through population-level studies that track vaping’s influence on smoking trends over time, especially since young people may frequently switch between vaping and smoking.

Findings on vaping’s role in smoking cessation were mixed. While some individuals take up vaping to quit smoking, several Tier 1 studies suggested that e-cigarette users had lower odds of quitting smoking altogether.

Conclusions

The study ultimately states, "The only thing that can be said with certainty is that the evidence is not certain." While some population-level studies were less biased than others, all individual-level studies carried a serious or critical risk of bias. Individual-level studies may be particularly prone to confounding variables based on personal factors.

The review of individual-level studies suggested—albeit with very low certainty—that young people who vape are more likely to progress smoking. Conversely, population-level data indicated, with equally low certainty, that as more young people vape, the overall rate of subsequent smoking decreases.

Past research has suggested that vaping predicts later smoking, but it has not provided strong causal evidence or incorporated population-level data. This study highlights that the assumption of vaping leading to smoking is not based on robust evidence and may evolve with further research.

Future studies are needed to establish clearer causal relationships between vaping and later smoking at both the individual and population levels. A more comprehensive understanding will be critical in informing public health policies and regulations.