E-cigarettes have sometimes been marketed as a way to cut back on tobacco use. But they offer no sure protection. In fact, a striking age gap has emerged in e-cigarette use. High-nicotine e-cigarettes have become increasingly popular among young adults who vape, and that shift may be making it harder for them to stop.

Young adults are much more likely than older adults to use high-nicotine products, and these stronger products are associated with greater nicotine dependence and a lower likelihood of quitting vaping, a national study tracking tobacco use in the United States has found.

The study reviewed data from the Population Assessment of Tobacco and Health (PATH) Study, a nationally representative survey from 2017, 2019, 2021 and 2022. It also tracked over 2,350 adults who vaped in 2019 to see how their behavior changed during the following four years.

High-nicotine e-cigarettes can make quitting more difficult. People who vaped using high-nicotine e-cigarettes had 31 percent lower odds of being abstinent from vaping four years later.

In 2017, the threshold defined as high nicotine was an e-cigarette containing at least 4 percent nicotine. Fewer than 4 percent of people who vaped reported using products containing this amount. Since then, nicotine concentrations have climbed. Among daily vapers ages 18 to 24, use of these products rose from 3.1 percent in 2017 to 40.1 percent in 2019, reaching 49.2 percent in 2022.

The contrast with older adults was pronounced. In 2022, 32.8 percent of daily vapers ages 25 to 34 used high-nicotine products, as did 17.6 percent of those ages 35 to 54. Among daily vapers ages 55 and older, the figure was 4.5 percent. Looking at people who vaped, researchers found that 18- to 24-year-olds had 12 times the odds of using high-nicotine e-cigarettes compared with adults 55 and older.

The increase coincided with a rise in nicotine dependence among young adults who exclusively vaped. In 2017, their dependence scores were substantially lower than those of young adults who exclusively smoked cigarettes. By 2022, the scores had risen to a level comparable to that of young adults who smoked exclusively in 2017. Across age groups, people using high-nicotine products reported greater dependence than those using lower-nicotine e-cigarettes.

Higher nicotine strength was associated with more persistent vaping, the study found. Among people who vaped in 2019, those choosing high-nicotine e-cigarettes had 31 percent lower odds of being abstinent from vaping four years later. Overall, 40.9 percent of the group — including people who did not vape every day — had quit vaping by 2022.

Across age groups, people using high-nicotine products reported greater dependence than those using lower-nicotine e-cigarettes.

“The Food and Drug Administration's (FDA) authorization of these products was based in part on the expectation that the benefits to adults who smoke would outweigh the risks of creating new nicotine dependence among young people,” said John P. Pierce, PhD, the study's senior author and a professor at the University of California San Diego Herbert Wertheim School of Public Health and Human Longevity Science. “Our findings suggest that this balance needs to be reassessed.”

The researchers also found that younger adults were more likely than adults 25 and older to choose high-nicotine versions even when using the same brands. Two brands showing especially large age differences had been marketed through paid social-media influencers. However, the study was not designed to determine whether marketing caused young people to select stronger products.

The findings do not prove that high-nicotine e-cigarettes caused dependence to increase. This was an observational study, not a randomized trial, and many participants, particularly those early in the study, did not know the nicotine strength of their products. That uncertainty may have led researchers to underestimate high-nicotine use.

Still, the pattern raises questions about how e-cigarettes are designed, marketed and regulated. The authors say regulators should reassess whether the potential benefits for adults who smoke outweigh the risk of creating nicotine dependence among young people. For consumers, the study underscores that vaping products vary in nicotine strength and that stronger products may be associated with a greater struggle to stop.

Pierce said researchers need to better understand how nicotine content, product design and marketing shape long-term use. The study cannot settle every question about vaping and quitting, but it documents a sharp generational divide in high-nicotine use — and a clear link between stronger products and dependence.

For anyone who vapes, the takeaway is that nicotine strength deserves attention. Although the study doesn't prove that stronger products cause dependence, it adds to concerns that high-nicotine e-cigarettes may make stopping more difficult. Understanding what a product contains is an important first step toward making informed decisions.

The study is published in Tobacco Control.