The research was carried out by a team at the TobaccoFree Research Institute Ireland (TFRI), in Dublin. They examined data on 6,216 teens aged 17 to 18 years, including information on whether their parents smoked while they were growing up.

The teenagers were asked whether they smoked or used e-cigarettes.

The study showed that teens whose parents smoked were around 55 per cent more likely to have tried e-cigarettes and around 51 per cent more likely to have tried smoking.

The team also combined several Irish data sets to provide the most comprehensive analyses of teenage e-cigarette use in Ireland, with information on more than 10,000 Irish teenagers, aged 16-17, to look at the overall numbers of teenagers trying or regularly using e-cigarettes and how this is changing over time.

This showed that the proportion who had tried e-cigarettes had increased from 23 per cent in 2014 to 39 per cent in 2019.

The main reasons teenagers gave for trying e-cigarettes were curiosity (66 per cent) and because their friends were vaping (29 per cent). Only 3 per cent said it was to quit smoking.

The proportion who said they had never used tobacco when they first tried e-cigarettes increased from 32 per cent in 2015 to 68 per cent in 2019.

Professor Luke Clancy, TFRI director general explained, "We have found increasing use of e-cigarettes in Irish teenagers and that's a pattern that is emerging elsewhere in the world.”

“There's a perception that vaping is a better alternative to smoking, but our research shows that this doesn't apply to teenagers who usually haven't tried cigarettes prior to e-cigarettes. This indicates that, for teens, vaping is a route into nicotine addiction, rather than out of it,” Clancy added.

Finally, the researchers looked in detail at data on 3,421 teens of 16-year to see if there were differences between boys and girls. Although boys were more likely to try or use e-cigarettes, the researchers found that rates were increasing more quickly among girls.

In 2015, only 23 per cent girls admitted of having tried e-cigarettes and it rose to 39 per cent in 2019. Only 10 per cent of girls said they were currently using e-cigarettes in 2015, rising to 18 per cent in 2019.

Researchers found that having friends who smoke and having less parental monitoring were both major factors in teenage use of e-cigarettes, more so for boys than girls.

Doctoral researcher Salome said, "We can see that parents and friends have an influence on teenagers' decisions to try e-cigarettes and that's important because these are factors that we can try to change.”

“However, governments need to play their part by making laws to protect children and young people. We already do this with smoking and we need to do the same with vaping,” Salome added.

Lead researcher Joan Hanafin stated, "We can see that the number of teenagers using e-cigarettes is changing fast, so we need to keep monitoring the situation. We also plan to study social media to understand how this influences girls' and boys' vaping behaviour."

Professor Jonathan Grigg, chair of the European Respiratory Society's Tobacco Control Committee who was not involved in the research says, "These findings are worrying, not just for teenagers in Ireland, but for families all around the world.

“We know already that children of parents who smoke are more likely to take up smoking. This study suggests that teenagers are also influenced by smoking parents to start using e-cigarettes and become addicted to nicotine,” he added.

Grigg added, "This work indicates that more and more teenagers are trying e-cigarettes and they are not doing so to help them quit smoking. This is important because we know that e-cigarettes are not harmless.”

“The effects of nicotine addiction are well-established, and we are discovering that e-cigarettes can harm the lungs, blood vessels and brain. We need to do more to protect children and teenagers from these harms,” he said further.