Phantom Gateway: Kids Who Ever Try Stuff Are More Likely to Ever Try Other Stuff

Here we go again.  The journal Pediatrics just published a study claiming that e-cigarettes are a gateway to cigarettes.  In fact, the report simply demonstrates that kids who ever tried one tobacco product are more likely than never triers to ever try another tobacco product (abstract here).

The current study, by Jessica Barrington-Trimis, Ph.D., and co-workers, is a follow-up on research published in the same journal in 2015 (abstract here).  In that work, the authors surveyed 2,084 11^th and 12^th graders and found that 499 (about 24%) had ever tried an e-cigarette (even one puff), while 390 (19%) had ever tried a cigarette (table below).

Ever E-cigarette and Cigarette Use (Even One Puff) Among 11th and 12th Graders in Southern California, 2014
	E-Cigarettes
Cigarettes	Ever	Never	Total
Ever	286	104	390
Never	213	1,481	1,694
Total	499	1,585	2,084

Notice that 286 kids had ever used both cigarettes and e-cigarettes in 2014, which is the majority for both products.  In other words, ever trying both products was common. 

Now let’s turn to the current study.  Sixteen months after the original survey, Dr. Barrington-Trimis sent follow-up surveys to the 213 students who had ever used e-cigarettes and never smoked, and to a sample of the 1,481 students who had never used either product.  She found that ever e-cigarette users were more likely to have ever smoked a cigarette – an unsurprising finding, given that we already know that trying one of these products is highly correlated with trying another.

Indicating a research bias, the authors did not look at the other important group – the 104 students in 2014 who had ever used cigarettes and never used e-cigarettes.  Did these smokers try e-cigs in the subsequent 16 months, and was that correlation weaker or stronger than the one reported? 

Responsible research should entail examination of all correlations, and public health policy should only be based on uncompromised, comprehensive data.