We’ve been hearing a lot about the possible gateway effect that e-cigarette use may have on susceptible teenagers: if they start vaping, it will lead to smoking later on. This, along with the “it looks like smoking” argument, is used to justify harsh restrictions on e-cigarettes even in the absence of evidence that they are harmful to your health.

So far, however, there is not much evidence of such a gateway effect for e-cigarettes. The ASH Survey conducted by YouGov found that only .1% of adults used e-cigarettes regularly but had never smoked. The same study found that “The worry about children becoming gateway users also seems unfounded. 99% of aware, never-smoking 16-18 year olds have never tried an e-cigarette.”

Before any substance or product can be a gateway to anything, it has to have a high level of popularity among people who have never used the substance(s) that it’s supposed to be a gateway to. Even though the ASH study has not yet followed these never-smoking vapers to see whether they do, in fact, take up smoking, I would not be putting my money on e-cigs as the top of my marketing funnel if I were trying to sell traditional tobacco cigarettes to non-smokers.

Arguments for a gateway effect seem to be predicated on the fact that most teens who use e-cigarettes also smoke, and the number of teens who use e-cigarettes is growing. Yet the CDC reports that during the same period that e-cigarette use among high school students increased from 1.5% to 2.8%, cigarette smoking fell from 15.8% to 14.0%, and overall tobacco use (in which e-cigarettes are included) fell from 24.3% to 23.3%. That doesn’t seem to support the idea that e-cigarettes are creating hordes of new smokers.

Furthermore, adult vapers who start using second-generation or better products often find that they can no longer physically tolerate smoking. They cough; they get dizzy; they feel sick. And these are people who smoked more than a pack a day for years. How is a first-time smoker going to react, and why would s/he persist with the misery of a combustible cigarette when a more pleasant alternative is available?

I’d gotten about that far in my mental preparation for this post when another thought came to me. I was listening to a Freakonomics Radio podcast about the relative dangers of marijuana and alcohol. Stephen Dubner interviewed economist Jeffrey Miron, who said

So many people are concerned that marijuana is what is known as a gateway drug, that is once you use marijuana it makes you more likely to use other drugs. I don’t think there’s any evidence for it that I would regard as statistically credible. All that one can really document is that many people who use harder drugs did use marijuana before they used harder drugs. But a huge fraction of those who use marijuana never go on to use harder drugs. So the effect, if any, would appear to be quite small. And of course we can point out that almost everybody who goes on to use marijuana or alcohol say, started off on mother’s milk or McDonald’s French fries. So the prior use by itself we don’t think of as causal, it’s just that there does seem to be an evolution in the pattern for those people who end up going on to use harder drugs.

And that made me think “What if there’s no such thing as a gateway effect?”

So I did a little research. What I came up with certainly suggested that there’s no gateway effect for marijuana, that in fact this persistent myth is the equivalent of saying that because most members of the Hell’s Angels rode bicycles as children, owning a bicycle is a gateway to joining a motorcycle gang.

A 2012 article in AlterNet pointed to a study that claims the real gateway drug is alcohol: “The findings from this investigation support that alcohol should receive primary attention in school-based substance abuse prevention programming, as the use of other substances could be impacted by delaying or preventing alcohol use.” Yet you can make the same arguments about alcohol that you do about marijuana: millions of people use it and don’t go on to abuse hard drugs—even when they develop serious alcohol problems.

My favorite article was probably the one called “Is chocolate the real gateway drug?” I know some people for whom it was, people whose plan for not getting fat was to get a mini-fridge stocked with vodka and keep no food in the house, people who could keep the weight off just fine as long as they were freebasing cocaine.

A study at Princeton University published in Neuroscience and Biobehavioral Reviews in 2008 showed that rats given glucose (sugar) actually stimulates the same receptors as heroin. In fact, the effect was so similar to the heroin stimulation that when the rats were given naloxone, a medication that treats heroin overdoses, the rats experienced the same kind of withdrawal. Chocolate has a significant amount of sugar. In addition to sugar, chocolate also has two other neuroactive drugs, caffeine and theobromine. Chocolate not only stimulates the opiate receptors in our brains, it also causes a release of neurochemicals in the brain’s pleasure centers. Chocolate, like other drugs, if used in excess can lead to negative health effects such as type II diabetes, obesity, and high cholesterol. So this would indicate that chocolate can be a part of any discussion about legal drugs.

That fits in perfectly with my personal experience, but I am a reasonable person. Yes, everyone experiences sugar highs, and I do think we should be much more careful how much sugar we give children. But most people manage to use chocolate in moderation and don’t move on to shooting up heroin in order to stay off the chocolate. (If you think that’s desperate and insane, I invite you to consider the gastric bypass operation.) Again, it’s hard to prove the existence of a gateway effect.

Or what about energy drinks? Yes, it appears that high school students who consume Monster and Red Bull are at greater risk for use of alcohol, cigarettes, and “illicit drugs” than are those who merely drink Diet Pepsi (my own besetting vice). You can’t make this stuff up.

Where was that link to the collection of spurious correlations?

My search has not been exhaustive, but so far I have not found convincing evidence that any one substance is a gateway to any other.

If you want to prove that Substance A is a gateway to Substance B, you’re going to have to conduct a longitudinal study. You’re going to have to find a statistically significant population of, say, non-smoking teens who have just started vaping, and a control group of teens who match them in terms of gender, race, and socioeconomic status. You’re also going to have to control for possible confounding variables such as parents or siblings who smoke, relative availability and price of tobacco cigarettes versus e-cigarettes, and so on.

And then you’re going to have to follow both those populations for years. That means paying scientists and research assistants to go observe and interview them at regular intervals, to find out whether they are still vaping, quit vaping, started smoking, etc.

This will cost, pardon my English, a metric f*ckton of money.

And in order for the study to have any validity, the people conducting it have to be willing for their hypothesis to be proved wrong. That’s what makes it science. You form a hypothesis and test it. If the evidence contradicts the hypothesis, you change the hypothesis, not the evidence.

I don’t think most of the entities that have the funding to conduct such a study are willing to leave themselves open to the possible results.

If there’s no such thing as a gateway effect, then e-cigarettes can’t have one. That’s a very uncomfortable possibility for some people.

It is only a possibility. I haven’t conducted that longitudinal study. (And I’m not a statistical research scientist, so even if you gave me the funding, I’d be the wrong person to do it.) But it seems like a pretty sound hypothesis.