The media reports the results of sloppy vaping research, then quickly forgets them. We do not. What follows is a list of many of the low-quality studies that have investigated the alleged health risks of e-cigarette use. We'll regularly update this catalog of bad studies as necessary.
The past year has seen the publication of many studies alleging that e-cigarette use (vaping) carries very serious health consequences, everything from depression to erectile dysfunction and higher stroke risk. Each paper generated widespread media coverage, usually one news outlet duplicating the uncritical coverage of the last, giving consumers the false impression that vaping poses a greater health threat than it actually does. When we examined these studies in more detail, we identified their serious flaws and reported them to our readers.
But health reporters tend to obsess over a topic for a few days then forget it entirely, quickly moving on to the next exaggerated study. So in the spirit of developing a more comprehensive understanding of the health risks and benefits of vaping, here's a greatest-hits compilation of the questionable research that has hit the headlines in recent months. 
- Vaping causes brain inflammation?
“Study suggests e-cigarettes can cause brain inflammation — with flavors affecting severity,” Salon reported in April. Never averse to hyperbole, the progressive outlet continued:
Opponents of e-cigarettes have long argued for a ban on flavored vape products — which experts say played a critical role in a startling resurgence of underage nicotine addiction. New research just revealed chronic usage of these tantalizing flavors may have also caused a hidden epidemic.
“Startling Resurgence,” “hidden epidemic.” Dear Lord, please spare us your righteous wrath! This study must be truly horrifying. If only.
The paper actually found that six female mice “exposed to flavored JUUL aerosols for 1 and 3 months had significant neuroinflammation in the brain, as well as inflammatory modulation in the heart, lung and GI tract ...” This is certainly a result worth further investigation. If vaping does indeed cause or contribute to inflammation, consumers should know about it. That said, this paper shouldn't cause too much anxiety for now, and there's several reasons for that.
The researchers acknowledged that the inflammatory markers they found “were solely at the gene expression level.” Vapor exposure didn't actually harm the mice in any meaningful way. The authors went on to note that:
Contrary to our initial expectations, we did not find significant changes in autonomic tone or pulmonary function with daily, long-term JUUL aerosol exposure.
How's this for an alternate headline? “Vaping exerts no significant effect on pulmonary function, defying researchers' expectations.” It seems like that is the newsworthy result, yet no report on the study even bothered to mention it. This is a recurring theme in e-cigarette research: the authors overlook their most significant finding in favor of a tenuous association that reinforces the vaping-worse-than-we-thought narrative.
In any case, we need to remember that nicotine has anti-inflammatory effects in many cases. “It is well known,” the authors of a 2022 review noted, “that nicotine … stimulates the nicotinic acetylcholine receptor signaling anti-inflammatory pathway to reduce inflammatory responses, depression, attention deficit–hyperactivity disorder, cognitive deficits in schizophrenia, Alzheimer’s disease, and pain.” This doesn't mean any dose of nicotine is harmless under any circumstance, but it certainly complicates the simplistic story reporters told in the wake of this paper.
On a related note, the authors of the new study speculated that “several of our findings point to a ‘non-nicotine’ chemical flavorant component of the JUUL device that may be driving inflammatory changes in the brain.” The problem may therefore be limited to a single product or even a single chemical, and, again, that assumes the findings are indicative of actual harm. This paper offers little support for the widespread assault on nicotine vaping products, even if we take its conclusion at face value.
Finally, mice are not little people, as ACSH founder Dr. Beth Whelan was fond of saying. The study's senior author, Dr. Laura Crotty Alexander, anticipated this objection, telling Medical News Today, “I think we can get enough data from our animal models that it would give enough insight [to inform] parents and regulators and healthcare practitioners.” It's not clear why this is so, however. The research team actually had to speculate about why their model didn't generate the results they expected:
Our model is limited in that mice are primarily nose breathers and we used whole-body exposure, so it is possible that the extent of e-cigarette aerosol exposure at the level of the alveoli may be lower than in humans due to aerosol deposition within the nasal cavity.
They can't have it both ways. If the study generated practical insight, there should be no need to explain away its underwhelming results.
"Vaping doubled the risk of erectile dysfunction in men 20 and older," CNN reported last December. What they left out was that all the data gathered for the study was self-reported. Men were classified as having ED based on a 1-item question: “Many men experience problems with sexual intercourse. How would you describe your ability to get and keep an erection adequate for satisfactory intercourse?” Suffice it to say, this was far short of a reliable medical diagnosis.
The researchers also relied on study participants to report how much they vaped or smoked. Strangely, the study did not find a link between daily smoking and ED. It's not clear why only vaping would carry this risk, since cigarettes often contain more nicotine than the liquids consumed by vapers.
Experiencing ED is probably unpleasant, but suffering a stroke is, I assume, a truly frightening experience. So when the American Heart Association (AHA) announced that researchers had linked vaping to stroke risk, the media went berserk, reporting that “E-cigarette users have a 15% higher risk of stroke at a younger age than traditional tobacco smokers, according to preliminary findings.”
As it turns out, "preliminary" was the wrong word to use. The study was never published, though the authors were scheduled to present their results at the AHA's annual conference. They never did, and it could be because the results were less impressive upon closer inspection. While vapers suffered strokes earlier in life, smokers actually had a substantially higher overall risk, 6.75% compared to 1.09% for e-cigarette users.
The same month, November 2021, MSN reported that "The evidence against vaping is mounting, and a new study now links e-cigarettes with an increased risk for broken bones." This was a misleading summary at best. The researchers actually found that current vapers had a lower prevalence of fractures than former vapers. If vaping causes bone damage, why would quitting e-cigarettes be linked to more bone damage?
This example comes courtesy of the Truth Initiative. “Two health crises among youth — a mental health crisis and a vaping epidemic — pose increasing threats to a generation of young people,” the tobacco industry-funded activist group wrote in a September 2021 report. “While it is well known that nicotine harms developing brains … lesser known are the worrying connections between nicotine and mental health.”
TI acknowledged that "it is unknown whether a causal relationship between nicotine and mental health conditions exists," but much more can be said than that. It's actually quite likely that a link between nicotine consumption and depression exists; however, it probably runs in the opposite direction. People diagnosed with the depression smoke to alleviate their symptoms, because nicotine has a well-documented antidepressant effect.
Because many studies have documented the smoking cessation benefits of vaping, tobacco control researchers have simply changed how they measure success in studies of e-cigarettes. Smokers who switch from smoking to vaping are counted as having "relapsed" if they have so much as "one or two puffs" of a cigarette. We've examined two recent studies with this design. The problem here is that many smokers quit gradually, initially replacing some of their cigarette consumption with vaping, many of them ultimately giving up smoking entirely.
There's a “teen vaping epidemic”
This claim isn't based on bad research so much as it's based on no research at all. ACSH has always opposed minors using any nicotine-containing product whatsoever, but we have to be honest about what the data show. Two important conclusions leap out of the evidence we've gathered so far: a minority, roughly 20 percent, of high school students have reported vaping at some point. However, the majority of these individuals are former cigarettes smokers, according to the authors of a 2021 study. "This [result] is consistent with other recent research showing that declines in cigarette use have accelerated after the introduction of [electronic cigarettes]," they wrote.
A January 2022 study suggested that e-cigarette users may harm the respiratory health of those around them via "secondhand vaping." The conclusion may have been plausible were it not for this odd detail: most of the study participants who reported symptoms caused by secondhand vape exposure were "also likely to have personal use of tobacco or cannabis products or secondhand exposure to combustible products," the study authors explained.
The obvious question is, how do they know it was passive vaping that caused the symptoms when a majority of these individuals were exposed to tobacco and marijuana during the study?
Vaping has proved very popular among ex-smokers, myself included. As a result, it's smart for public health researchers to investigate the risks and benefits of e-cigarettes. Whatever danger vaping poses should be honestly reported to the public. That said, poorly designed epidemiological studies that make unreasonable assumptions or ask the wrong questions only muddle the discussion, leaving consumers misinformed about vaping. Hopefully we'll see less of this low-caliber research in the future. If not, this list will continue to grow.
 Did we miss any? Post your suggestions in the comments.