A new expert analysis has challenged claims that vaping has slowed progress in cutting youth smoking rates in Australia and New Zealand.
Recent academic papers from the University of Sydney’s Professor Becky Freeman and her team argue that the rise of vaping has “slowed the rates of decline in ever- and regular-smoking” among teenagers.
But another researcher says the evidence doesn’t support that conclusion, and that the studies rely on questionable assumptions.
What the papers said
The Sydney team’s findings were published this year in three journals.
- In New Zealand, a paper in The Lancet Regional Health – Western Pacific said that “the rapid rise of vaping may have slowed the rates of decline in ever- and regular-smoking, while having little or no impact on the rate of decline in daily smoking.”
- In Australia, a study in the Medical Journal of Australia reported that “there were.. more [12 to 17-year-olds] who had engaged in ever, past year, past month, past week and daily smoking than projected by smoking trajectories from the pre-vaping era.”
- A third paper, in Public Health Research & Practice, argued that even when both smoking and vaping fall at the same time, a “gateway” effect is still possible if vaping merely slows the pace of decline in smoking.
The message was that youth smoking is still falling, but not as fast as it would have without vaping.
The counter-argument
One expert, behavioural scientist Dr Arielle Selya, says those claims don’t hold up. Writing in her analysis of the papers, she notes that other researchers, including Dr Gary Chan and colleagues, have also criticised this assumption, writing that it “assumes pre-existing trends would have continued unchanged in the absence of an intervention.” The researchers’ models rest on a major assumption – that smoking rates would have continued to fall at exactly the same pace if vaping had never appeared.
That, she says, is “questionable, particularly for behaviours like smoking that start from high prevalence and flatten over time due to saturation effects.”
The authors responded that “the logistic regression accounts for this flattening.. The slowing we observed was above and beyond flattening due to saturation effects.”
But Dr Selya still isn’t convinced. Looking at the underlying data, she said she could see what she called a small “bump” in New Zealand smoking rates around 2019–2021, but added: “If e-cigarettes were causing a relative increase in smoking, why would the effect be delayed by nine years? And why would the effect be constrained to two years and then go away?”
In her view, the pattern is too brief and too late to pin on vaping.
Australia shows no sign of a change
When Dr Selya looked at the Australian data, she said she “does not see a visually-evident change in smoking trends.” Overall youth smoking continued to fall sharply – roughly 75 to 90 per cent across different measures since the late 1990s – and she suspects that the statistical “slowdown” reported by the authors may come from their choice of model rather than a real-world change.
She also pointed out that small shifts in the researchers’ cut-off year (the point at which vaping supposedly began to affect the trend) could easily change the outcome.
Other possible explanations
Dr Selya notes that many things besides vaping could have influenced the small uptick seen in some data. “Was this a COVID effect? Did these years correspond to key policy changes in Australia regulating the less-harmful product and pushing people to cigarettes?” she asks.
She says it’s risky to draw causal conclusions when “correlated time trends do not mean causation.”
A debate over methods – and meaning
Dr Selya stresses that she doesn’t doubt the technical skill of lead author Dr Sam Egger, calling him “very methodologically capable.” But she adds: “I found the interpretation so flawed that I wrote a PubPeer comment on it.”
The dispute may seem academic, but it has real-world implications. If vaping is wrongly blamed for slowing progress, governments might double down on restrictive policies that make it harder for smokers to switch to lower-risk products.
For now, both countries continue to record steep declines in youth smoking. Whether vaping has slowed those declines, or helped drive them, depends on how you read the data.
As Dr Selya sums up: “I do find it plausible that there was a bump in smoking in New Zealand youth, but.. I don’t think it makes sense to attribute this to e-cigarettes.”
