Posted: 2017-12-03 13:10:42

by Carl V Phillips

I have repeatedly tried to explain what gateway claims mean — that engaging in one behavior causes another behavior (in the present context, that vaping causes smoking), what they do not mean, and what constitutes valid evidence for or against their existence. Why bother? As I noted in a recent piece on the topic, for The Daily Vaper (which links back to some of my more in-depth pieces), “most of the claims by vaping proponents that there is no gateway effect are also nonsense.” Indeed, they create such a target-rich environment for criticism that even Simon Chapman can find the flaws.

He (or someone) recently posted an analysis he and David Bareham wrote about the recent J-F Etter paper in Addiction. On twitter, @jkelovuori (Jukka Kelovuori‏) called my attention to it and asked for my thoughts. I pointed out that it was generally valid. If a second-year student turned this in for an assignment, it would be B- material — even B if they took out the science fiction bits (see below). This made it a somewhat refreshing read compared to the average tobacco controller paper, which is a full-on F, or for that matter, compared to a lot of pro-vaping writing.

Chapman and Bareham made three main points. Two of them call out genuinely erroneous claims in the original paper. The third is a valid retort to some sloppy claims, but not to the real science that Etter presented.

To appreciate their critique, it is necessary to read it as science fiction. Proper science fiction makes up a few alternate facts about the world and then — in contrast with mere fantasy — stays realistic within those bounds. A story that posits faster-than-light travel can still offer insights about the human condition or the uncertainties of meeting aliens. It can even offer insights about the implications of FTL travel. It cannot, of course, demonstrate that FTL travel is possible — that is merely a premise.

In the present case, the authors spill most of their ink banging on about tobacco control’s usual fictitious premises: various anti-smoking measures are hugely effective, and also nicotine is magically captivating. (A good sci-fi author does not usually choose fictitious rules that are quite so close to being mutually-contradictory. I did not say these guys were writing good sci-fi.) If you read the critique and just gloss over these bits, it is not a terrible analysis.

(Of course, since I have written complete and thorough analyses of all these points, it is not entirely clear why anyone should bother with something that is merely not terrible. But let’s go ahead and break it down.)

Starting with the third of their points:

In criticising studies which do not differentiate adolescent occasional, experimental vaping from more regular vaping, Etter argues that it is “hardly plausible that a simple puff or a few puffs on an e-cigarette can cause subsequent regular smoking.”  But of course every regular smoker started with a “simple puff”, mostly in adolescence. …. Just as no young smoker commences their smoking career by smoking a pack on their first day, few if any adolescent vapers commence vaping with heavy, daily use.

It is indeed a common trope to criticize a gateway study for looking at e-cigarette trialers or ignoring intensity of vaping. This is nonsense. Chapman and Bareham do not quite get the critique right or finish it, but their intuition is right. (Do not bother to read beyond that quote, expecting them to complete the thought. They immediately spiral off into a full page of mysticism about nicotine. Good sci-fi writers do not engage in asides about their conceits; they feed the necessary information to the reader organically.)

Not restricting the exposure measure to established vaping is fine, for a couple of reasons: (a) Someone might be claiming that any vaping, or that trialing in particular, causes smoking, and thus it is better to not restrict the exposure definition to dedicated vapers. (b) If the hypothesis is that dedicated vaping causes smoking, but not mere trialing, it can still be informative to look at trialers or a mix of usage intensity, if that is the data you have. Trialing vaping would cause smoking less often than dedicated vaping (which is the real hypothesized cause), because it is a weak proxy for dedicated vaping, but it would still cause smoking. Indeed any measured effect would underestimate the effect of dedicated vaping (this is called attenuation bias).

Of course this assumes that a study does not have other fatal flaws that make its results meaningless; every study to date has such flaws.

Chapman and Bareham, as nonscientists and non-readers (I have presented that analysis about attenuation from proxy measures of vaping exposure in greater detail), do not seem to fully understand this. But they still realized that the trope is wrong and have some intuition about why, so I will give them substantial partial credit.

In their first point, Chapman and Bareham observe:

Etter repeats a frequently made argument that the gateway hypothesis is incompatible with evidence from the USA and UK of declining adolescent smoking. The argument here runs that vaping has been rising while smoking continues to fall, so vaping cannot be causing smoking to any significant degree at the adolescent population level.

This argument relies on an assumption that the population-wide net impact of any putative gateway effect of e-cigarette use would be larger than the combined net impact of all other policies, programs and factors which are responsible for reducing adolescent smoking prevalence….  This is a ridiculously high bar that gateway critics demand that anyone suggesting gateway effects must jump over.

A spot-on takedown of what is probably the most common — and most obviously wrong — “there is no gateway” trope. We can just focus on “factors” and ignore the sci-fi claims about policies and programs. Anyone who recognizes that vaping replaces some smoking, and that we are still experiencing the echoes of the huge decline in smoking that resulted from universal knowledge of the harms, should see that this is true.

Of course, Chapman and Bareham do not mention those most obvious and defensible explanations for the net decline. Instead they go on to cite the junk science about implausibly large effects from tobacco control policies and programs. Thus their core argument is solid, but attempt to further support it fails.

This is where the sci-fi metaphor gets interesting. If someone does accept their conceit — that tobacco control policies and programs are having a big effect — they must concede that “but prevalence is declining so…” is nonsense. Yet some of the loudest proponents of that nonsense are pro-vaping tobacco controllers who claim to believe tobacco control policies are effective. This makes their error even more embarrassing.

Chapman and Bareham’s second point is a bit more complicated to analyze correctly. Under the heading, “Double standards on gateway and ‘reverse’ gateway effects?”, they argue:

E-cigarette enthusiasts often argue that vaping is demonstrably a reverse gateway out of smoking for those who quit, while being scathing about suggestions that it could ever be a gateway into smoking.

Soundbites like “kids who will try stuff, will try stuff” and “kids who will smoke, will smoke” have been repeatedly held aloft like an omnipotent crucifix before a gateway vampire. These responses are voiced as self-evident truisms, with their circularity being seductive at first blush. However, any cessation researcher offering the equally trite “smokers who will quit, will quit” as a serious contribution to understanding the complexity of transitioning out of smoking, would be rightly pilloried….

Their heading is silly, even if you set aside the bad phrasing about “reverse gateway”. (Another minor criticism of some anti-gateway claims: The jargon “gateway” is a lousy metaphor, but it has an established meaning. Playing games with terminology — saying it is a “gateway out” and whatnot — has no place in scientific debate.) Calling it a “double standard” that people believe some assertions and doubt others is some epic weak thinking.

Also, apparently Chapman cannot resist going a few pages without engaging in his preferred style of debate, which is the semi-adult version of saying “nyah nyah, you said….” In this case, he intentionally misconstrues a statement that obviously really means “kids who will try one thing are likely to try another” as being circular because of how it is often phrased.

But there is something that approaches validity at the core here. We can salvage their mess by rewriting the claim using some actual science: “often, gateway opponents claim ‘kids who try some stuff will inevitably try other stuff’ but they just assert this is self-evidently true, and imply this assertion alone sufficient to deny there is a gateway effect.”

This challenge to the incompleteness of the argument has nothing at all to do with whether or not someone dismisses the “all vapers would have quit anyway” claim (though any sensible person does dismiss that, obviously). That is pure red herring.

This turns out to only be a criticism of the vague hand-waving way in which the claim is sometimes made. It is not a criticism of the underlying claim when it is properly supported. Consider the point rewritten in scientific terms: “There is good reason to believe that strong confounding will create an association between vaping and smoking, so a lot of work has to be done before claiming an association is causal.” That is the main theme of my major paper on this topic (see first link).

This is not presented as a “self-evident truism”, like when people invoke meaningless phrases like “the common liability model”. We know — from evidence — that kids who try one drug, delivery system, or other forbidden/risky behavior are more likely than average to try another. This is pretty much true for whichever two of these you pick, even those that seem unlikely to be causally related (e.g., motorcycling and smoking). This is evidence of confounding.

For vaping and smoking, not only are the two behaviors both forbidden sensation-seeking, but they are use of the same drug. Obviously there will be even more confounding there. A third to half of the population dislikes consuming nicotine. They will avoid trying more than a puff or two of either product. This alone creates confounding — anyone who vapes beyond a puff or two is identified as (not caused to be!) someone who would not hate smoking.

For those who understand how epidemiology statistics work, there is further evidence still. The studies of these associations always include “control” covariates in the analysis. This means that even the researchers who are trying to show a gateway effect are admitting that there is confounding. They then — in an error that is common to most public health research — implicitly claim that they statistically eliminated its effects (“controlled for it”). But they did not.

Consider the confounding that is created by some people not liking nicotine. A perfect dataset would have a measure for that, in which case it could be a control variable (or, better still, a stratification variable). Instead, they probably just controlled for age, sex, SES, and such, which offer basically no measure of this. The best-case scenario is that they have a measure of parental smoking, which seems to be a predictor of taste for nicotine. But obviously this is a very noisy proxy for “taste for nicotine” so controlling for it might control for some of that particular source of confounding, but some will remain (“residual confounding”). Similar observations apply to attempting to control for confounding caused by willingness to break the rules, being more socially active, and so on.

The bottom line is that this confounding need not be self-evident because it is overwhelmingly evident in the data and specific existing knowledge. Thus Chapman and Bareham are ultimately presenting a strawman argument (another Chapman favorite). Indeed, Etter is not among those who suggest it is self-evident. He identifies this as a confounding problem and explains why it is a problem — not perfectly, but he basically touches on most of the key points.

This strawman keeps Chapman and Bareham from being a candidate for an B+ grade. The confounding problem, alone, is why existing research provides no evidence of a gateway effect. Etter’s paper has flaws — the two that Chapman and Bareham identified and others — but it also contains the key valid argument. If Chapman and Bareham were writing a generic criticism of anti-gateway broadsides, they would be right in noting that the confounding argument is usually unconvincing as presented. But it is not a fair criticism of Etter’s paper.

But overall, they got most of the criticism almost right, which is not too bad for amateurs.

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