Review of: Abigail S. Friedman, “A Difference-in-Differences Analysis of Youth Smoking and a Ban on Sales of Flavored Tobacco Products in San Francisco, California,” JAMA Pediatrics (2021).
Reviewed by: Chelsea Boyd

In response to continued concern over youth vaping rates, some jurisdictions have implemented flavor bans in an attempt to make nicotine products—combustible cigarettes, vaporizers (vapes), e-cigarettes and other electronic nicotine delivery systems—less appealing to young people. The ban in one jurisdiction, San Francisco, enabled researchers to evaluate what happens to youth smoking rates following a ban on flavored tobacco products.

Using data from the Youth Risk Behavior Surveillance System (YRBSS) 2011-2019 school district surveys, the researchers conducted a difference-in-differences analysis. The sample included students under the age of 18 from New York City, New York; Broward County, Florida; Los Angeles, California; Orange County, Florida; Palm Beach County, Florida; Philadelphia, Pennsylvania; San Diego, California and San Francisco, California. Of the surveyed locations, San Francisco was the only jurisdiction that banned flavored tobacco products.

The researchers compared past 30-day smoking rates in San Francisco to past 30-day smoking rates in the other jurisdictions. From 2011 through 2017, the proportion of students who smoked combustible cigarettes was approximately equal in San Francisco and the other jurisdictions. However, after San Francisco banned flavored tobacco products in June 2018, 2019 YRBSS data shows that youth smoking rates in San Francisco increased while the other jurisdictions continued to see declines. Specifically, youth in San Francisco were 2.24 times more likely to have smoked in the past 30 days compared to their counterparts in other jurisdictions. The difference-in-differences analyses were adjusted for differences in age, sex, race/ethnicity, combustible cigarette tax rate and smoke-free restaurant laws to minimize the impact of demographic differences.

As a check for robustness, the researchers limited the comparison group to jurisdictions in California. Here too, they found that youth in San Francisco were twice as likely to have smoked in the previous 30 days compared to young people in San Diego and Los Angeles. Since this analysis used a smaller sample size (which makes it more difficult to detect differences between groups) and minimized the demographic differences between the groups of students surveyed, the result indicates that the flavor ban was associated with an increase in youth smoking.

There are some limitations to this study. For one, it is unclear if the results will generalize to other areas that implement flavor bans. Another limitation is that the study did not assess the effect of the flavor ban on vaping. The authors did not include vaping in their analysis because the YRBSS data does not distinguish between vaping cannabis and vaping nicotine, which could lead to inconsistencies or inaccurate measurements because California legalized cannabis the same year San Francisco banned flavored tobacco products.

With jurisdictions across the country considering e-cigarette flavor bans and an imminent federal ban on menthol cigarettes, this study adds to the conversation about the utility of flavor bans at a vital time. For policy changes to be effective, it is important to understand if bans on flavored tobacco products produce the desired outcomes. Although decreasing youth vaping rates is a noble goal, policies that unintentionally increase the smoking rate among young people or adults create a bigger and more dangerous problem than the one they are trying to solve.

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