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>> The JAMA Network.
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>> Hi. I'm Adam Leventhal, Associate Professor and Director of the Health, Emotion,
and Addiction Laboratory within the Keck School of Medicine
at the University of Southern California.
E-cigarettes are battery-powered devices which heat up a solution
that usually contains nicotine and some other chemicals
into an aerosol that can be inhaled by the user.
The major intended purpose of e-cigarettes, initially, were to help adult smokers
who were looking for a way to back alternative.
And e-cigarettes could potentially help them cut down or even quit smoking.
There's also a corresponding evolution in the popularity of e-cigarettes
such that were seeing quite an extensive increase in the use
of e-cigarettes nationally among teens primarily for recreational purposes.
So even teens who have never even smoked before, a lot of them are using e-cigarettes.
If they use e-cigarettes and they enjoyed the experience of inhaling nicotine,
it's possible that they might be more open to trying other tobacco products
like conventional cigarettes and other smokable tobacco products.
And of course, that's a major public health concern.
So the objective of this study was to see whether teens
who use e-cigarettes are more likely to start smoking than teens who don't.
We partnered with 10 schools in the Los Angeles Metropolitan Area, and back in 2013,
we invited all teens who were enrolled in those schools
who were ninth graders to complete surveys.
We selected 2530 of them who reported
that they had never tried any smokable tobacco product at the beginning of ninth grade.
And we followed that group.
We came back and gave them another survey six months later at the end of ninth grade.
And then a third survey a year later.
And the primary aim was to compare the teens who had used e-cigarettes to those who hadn't
at the beginning of ninth grade in terms of the likelihood of starting
to smoke a combustible tobacco product over that 12-month follow-up period.
The teens who used e-cigarettes were more than 4 times more likely to start smoking
over the follow-up period than the teens who didn't use e-cigarettes.
This was consistent over every tobacco product we studied.
And we looked at a number of factors that could potentially account for this association
as co-variants in the study, including demographic factors.
We also looked at personality traits like impulsive tendencies.
We also asked questions like, 'Do you think that you'll start smoking over the next six months?
Or, 'If your friends offered you a cigarette, would you be willing to try it?'
And, even we statistically accounted for all of those factors that are known risk factors
for smoking initiation, we still found consistent associations between e-cigarette use
and the likelihood of starting smoking.
So while we found consistent associations, because this is an observational study,
we can't conclude that there is a causal effect here.
In other words, we can't conclude
that e-cigarette use directly leads to smoking initiation.
But what we can say is there is an association, and we need to follow this
up with future studies to see whether this association may indeed be causal.
And a remaining question is whether e-cigarette use is associated with the propensity
to become a regular, heavy smoker who, perhaps, is addicted to tobacco cigarettes
and other combustible tobacco products.
One of the things that we like to do is develop prevention programs
that can educate teens about, you know, what are in these e-cigarette products
and what are the potential consequences.
And if we could do that, we potentially could have some really important downstream
consequences for public health and preventing smoking-related disease.