One of the major concerns some public health experts have with the rise in use of electronic cigarettes is that they could act as a "gateway" to the use of traditional tobacco products. A study of high school students has now suggested that those who use electronic cigarettes may indeed be more likely to begin smoking.

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Use of e-cigarettes has risen sharply in recent years, including among adolescents.

The study, published in JAMA, followed 2,530 students from 10 public high schools in Los Angeles, CA, for a year. Each student reported having never used combustible tobacco, such as cigarettes, cigars or hookah, at the start of the study.

Recent estimates cited by the researchers suggest that 16% of 10th graders in the US had used electronic cigarettes (e-cigarettes) within the past 30 days. Of these students, 43% reported having never tried traditional cigarettes.

E-cigarettes are small devices typically comprised of a battery, a cartridge holding a liquid solution and an atomizer that vaporizes the solution. Solutions within the cartridges usually contain nicotine and concentrations can range from very little to 24-36 mg/ml.

At present, it is unknown if e-cigarette use increases the risk of an individual going on to start using combustible tobacco products, and this remains a point of contention within the debate

The study began in fall 2013 when the students were in 9th grade. A total of 2,530 students who reported having never used combustible tobacco products completed follow-up surveys after 6 months and 12 months. The surveys asked whether they had used combustible tobacco products over the past 6 months and, if so, how many different types.

At this time, adolescents adjust to the transition from middle school to high school and experience a period of uneven brain development. The researchers suggest that, as a result, the expression of a propensity to start using combustible tobacco products may be heightened during this time.

A total of 222 participants reported having used e-cigarettes at the start of the study, compared with 2,308 who had never used the devices.

After 6 months, 31% of the students who had used e-cigarettes reported having using combustible tobacco products compared with 8% of those who had never used the devices. After 12 months, 25% of the students who had used e-cigarettes reported having used combustible tobacco products compared with 9% of those who had never used the devices.

After adjusting their findings for sociodemographic, environmental and psychological risk factors, the researchers concluded that the students who reported having used e-cigarettes at the start of the study were more likely to have gone on to use any combustible tobacco product than the baseline e-cigarette never users.

Transitioning from e-cigarettes to traditional cigarettes

The researchers state that their findings provide new evidence that, over time, e-cigarette use is associated with an increased risk of combustible tobacco use initiation during early adolescence.

They hypothesize why some of the students were more likely to use e-cigarettes before traditional tobacco products:

"Some teens may be more likely to use e-cigarettes prior to combustible tobacco because of beliefs that e-cigarettes are not harmful or addictive, youth-targeted marketing, availability of e-cigarettes in flavors attractive to youths, and ease of accessing e-cigarettes due to either an absence or inconsistent enforcement of restrictions against sales to minors."

Study author Adam Leventhal, associate professor of preventive medicine and psychology at the University of Southern California, Los Angeles, told Medical News Today that it is possible teens who use e-cigarettes may enjoy the pleasurable effects of inhaling nicotine from the devices.

"As a result, they may be more open to trying other products that provide inhaled nicotine, like smokeable tobacco products," he said. "Future research is needed to evaluate whether such a process explains the association of e-cigarette use and smoking initiation we observed."

Leventhal stated that although the findings of their observational study are suggestive, there is not enough scientific evidence available at present to definitively determine whether e-cigarette use leads to use of smokeable tobacco products in teens.

In many countries where e-cigarette use among children has risen, rates of smoking among young people have declined. Dr. Penny Woods, chief executive of the British Lung Foundation, says that this fact counters claims that e-cigarette use is a gateway to the much more harmful practice of smoking.

"Regular e-cigarette use among children remains rare, but rising rates reinforce the need to monitor this area closely," she adds. "Many adult smokers find e-cigarettes to be a useful means of quitting smoking, but the lack of data on their long-term health impact means we would not recommend them to children or non-smokers."

Previously, MNT ran a Spotlight feature examining the debate around e-cigarettes and whether or not people should be worried about using them.