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Chinese pharmacist Hon Lik had good reasons for inventing the first commercially viable electronic cigarette. His father died of smoking-related lung cancer, and Hon himself tried unsuccessfully to quit using the nicotine patch. One night in 2003 he dreamed he was drowning in a sea that turned into a cloud of vapor, and awoke inspired to create a safer product based on liquid vapor, rather than combusted smoke. He received a patent for the device in 2007.

Since then, an estimated 250 e-cigarette brands have become available in the United States alone. Use nearly doubled among adults from 2010 to 2011 — from 3.3 percent to 6.2 percent in Web-based surveys, or about 15.5 million people — and more than doubled among minors from 2011 to 2012, according to the Centers for Disease Control and Prevention. Wells Fargo Bank tobacco analyst Bonnie Herzog has predicted that e-cigarette sales will outstrip regular cigarette sales within a decade.

But are e-cigarettes safe? So far, that question remains unanswered. On the individual level, they appear to be much less harmful than traditional cigarettes, and as such, have the potential to serve as a relatively healthy substitute for people who smoke — provided they quit smoking, say tobacco experts, including Johns Hopkins University School of Medicine psychologist Jack Henningfield, PhD, who also is vice president of Pinney Associates, a consulting firm that addresses issues related to the science of tobacco and pharmaceuticals. (In January, the company signed an agreement with Sottera, which manufactures the e-cigarette NJOY, to provide them with scientific, regulatory and policy support to encourage regular adult smokers to adopt these devices as an alternative to combusted tobacco.)

But concerns remain. Among them is a lack of regulation, since there are no specific quality control standards on e-cigarettes, except those that apply to all consumer products. Relatedly, critics are worried about contaminants. And there are questions about e-cigarettes' long-term health effects and the potential dangers of second-hand vapor.

More to the point for psychologists are behavioral concerns and how to minimize them. Studies to date have not shown regular use among non-smokers, but how can researchers and policymakers make sure e-cigarettes won't act as "gateways" to traditional smoking for kids who never smoked before? Or that people won't use them for more nefarious purposes, such as carriers for drugs more potent than nicotine? For these reasons and more, psychologists in the field — most or all of whom are also public health advocates — are concerned that data on individual behavior may not translate to the population level. In other words, will 10 percent or 90 percent of people use e-cigarettes as a bona fide way to quit smoking? Or will most use them as stopgaps for times when they're not allowed to smoke?

However these questions are answered, one thing is certain: Because of the lack of appeal of nicotine replacement products like gum and patches — they're expensive, available only in pharmacies and often not used as directed — e-cigarettes hold a lot of promise as a new way to help smokers quit or reduce conventional smoking.

"It's the first time in 100 years that we've had a real harm-reduction alternative," says psychologist David Abrams, PhD, of the Schroeder Institute for Tobacco Research and Policy Studies, Johns Hopkins' Bloomberg School of Public Health and the Georgetown University Lombardi Comprehensive Cancer Center, who expands on the topic in a Jan. 8 editorial in the Journal of the American Medical Association. "There's every indication that e-cigarettes may be both a safe and appealing way to get your nicotine."

What are e-cigarettes?

E-cigarettes — also known as ENDS, or electronic nicotine delivery systems — look and act a lot like regular cigarettes. They're plastic or metal rods that can light up at the end and release vapor that looks like smoke when puffed — an action popularly called "vaping." When users inhale, they get a nicotine hit.

Unlike combustible cigarettes, though, they have a battery-operated heating element and cartridge that contains nicotine, water, glycerol, propylene glycol, flavorings, and in some cases, trace amounts of other potentially dangerous ingredients, like metals. Puffing on the device activates the heater, which vaporizes the nicotine solution.

They are believed to be safer than conventional cigarettes largely because they don't deliver toxic elements like tars and carbon monoxide through burning. (While nicotine is addictive, it does not harm adult health at the amount delivered in smoking or vaping.) But it's their design that makes them appealing to would-be quitters, says Jean-Franc¸ois Etter, PhD, a public health professor and tobacco researcher at the University of Geneva in Switzerland.

"E-cigarettes provide nicotine, and they also provide flavor, the gesture, the throat hit that smokers want, and the visible vapor — all of these things together explain why the product is so successful."

That said, the devices have been unregulated at the federal level since their introduction in the United States in 2007, though some states, counties and cities do have standards in place relating to minors. In a 2010 court case, the e-cigarette manufacturer Sottera argued successfully that the products are tobacco products, not therapeutic devices. That means they don't have to undergo painstaking testing by the Food and Drug Administration, or be marketed only as smoking-cessation devices. The FDA is due to announce plans to regulate e-cigarettes as tobacco products in the near future, but until then, anyone can buy them — including minors if they do so over the Internet.

Studies underway

A number of complex issues make e-cigarettes both an intriguing and a thorny subject to study. One is that many e-cigarette smokers still use traditional cigarettes — called "dual use" by researchers — leaving it unclear whether adding e-cigarettes to their repertoire results in a net gain or loss of health.

"It would be good news if dual use were just a transition period — if people were acclimating themselves to e-cigarettes but, over a period of weeks or months, were transitioning completely to e-cigarettes," says Tim McAfee, MD, director of the CDC's Office on Smoking and Health. "But we have considerable reason to be concerned this might not be the case for a large number of users."

Others, like Abrams, counter that because e-cigarettes are clearly different from conventional cigarettes, they may further de-normalize conventional smoking and even speed its demise.

Meanwhile, McAfee and others also are concerned that e-cigarette advertising — which likewise lacks specific regulations, with some ads looking a lot like the seductive cigarette ads of the past — could minimize the substantial gains made in preventing youth tobacco uptake or convince more smokers to become vapers.

"If you watch someone using an e-cigarette in some ads and you didn't know they were using an e-cigarette, you'd think they were smoking," says McAfee. "We're worried that this kind of imagery may help break down barriers for adolescents." Other experts think the ads could attract smokers desiring to quit who would otherwise not have been able to stop.

Despite such concerns, research shows some hopeful signs about the products, including findings about their dual use. A 2013 study reported in Addictive Behaviors by Etter and Christopher Bullen, MD, PhD, of New Zealand's National Institute for Health Innovation, found that of 477 people they surveyed on e-cigarette and smoking cessation forums, 22 percent of dual users had stopped regular smoking after a month and 46 percent of the remaining sample had quit after a year.

Similarly, the Toolkit Study, a major smoking-cessation study in England, found that the number of people who used e-cigarettes to help them quit regular cigarettes increased 30 percent from 2012 to 2013. And in a study of 650 would-be quitters reported in the Nov. 16, 2013, Lancet, Bullen and colleagues found that nicotine-based e-cigarettes were as effective as nicotine patches in helping people stay smoke-free over 13 weeks. They were no less healthy than patches, and participants found them more appealing.

Psychologist Robin J. Mermelstein, PhD, of the University of Illinois at Chicago, is finding that image, too, is a big draw for e-cigarette users between ages 18 and 24 — a prime target for advertisers. In preliminary observations from an ongoing two-year National Cancer Institute study on young adult e-cigarette use, Mermelstein is finding that "young adults find e-cigarettes intriguing and cool." They like the chance to become "connoisseurs" by filling the e-cigarettes with hand-selected liquids, for instance, or using distinctive terminology to talk about them.

Such findings help explain why, even though e-cigarettes are not problem-free, they could be considered a viable harm-reduction or quitting option for those who continue to smoke, says psychologist Dorothy Hatsukami, PhD, a tobacco researcher at the University of Minnesota. "Even if they have comparable efficacy [to other quitting methods], there may be more smokers willing to try them," she says. "If that's the case, there may be more smokers trying to quit and even succeeding in quitting." 

Nicotine uptake

Other researchers are looking more closely at the product itself and how users interact with it. In one study, Virginia Commonwealth University (VCU) psychologist Thomas Eissenberg, PhD, and colleagues asked 32 regular smokers who had never smoked e-cigarettes to vape, smoke, or otherwise puff on different products, including two brands of e-cigarettes, a traditional cigarette and an unlit cigarette.

The researchers measured participants' heart rate, blood nicotine levels and reported symptoms of withdrawal as participants puffed on each product 10 times, waited 90 minutes and puffed 10 times again. They found that neither e-cigarette delivered nicotine as effectively as puffing on a lit tobacco cigarette. The devices did, however, suppress withdrawal to some extent, suggesting that cues such as moving one's hand to one's mouth and inhaling and exhaling vapor may be enough to suppress craving and other withdrawal symptoms, Eissenberg notes.

Thanks to these unexpected findings, half of the results were published early, in a 2010 paper in Tobacco Control. (Full results can be found in another 2010 paper, in Cancer Epidemiology, Biomarkers & Prevention.)

The team then conducted another study published in Nicotine & Tobacco Research in January 2013, this time with experienced e-cigarette users. Many in this group received "cigarette-like" doses of nicotine, suggesting they had developed more effective ways of drawing in the vapor — a topic to examine in future studies.

In a newly funded five-year project (see sidebar), Eissenberg will examine other basic questions related to e-cigarettes, including their toxic effects over the long term and how their use influences cigarette use. He and colleague Robert L. Balster, PhD, will head the new Tobacco Center of Regulatory Science at VCU, one of 14 institutions to receive major federal grants in this area through a joint program of the NIH and FDA.

New choices on the shelf

On the public health level, researchers are using technology-driven methods to capture how the influx of e-cigarettes into the sales environment might influence people's buying habits. They're combining ecological momentary assessment, which prompts people to keep a regular record of their actions with cellphones or other mobile devices, with geographic information system technologies, which provide real-time information on users' geographic locations and link them to street-view photos and other information. The resulting data are used to study users' interaction with the rapidly evolving landscape of e-cigarettes and other non-combustible tobacco products.

The combination promises greater accuracy in understanding the influence of environmental factors on buying or smoking behavior, says psychologist Tom Kirchner, PhD, of the Legacy Foundation's Schroeder Institute, who is leading the development of the new methodology. 

Past studies have all been associative, using aggregated data on tobacco use from one source and pairing it with data on nearby tobacco outlets. "This data can be informative," says Kirchner, "but it does not allow study of each individual's point-of-sale experience."

Kirchner and colleagues tested the new method with 475 people attempting to quit smoking, using data on their movements to study contacts with tobacco outlets in real time. Their report in the October 2013 issue of the American Journal of Preventive Medicine found that people's contact with point-of-sale outlets was associated with smoking, and that visiting these outlets triggered them to smoke even if their craving was low.

Such data show the method "can identify previously unrecognized patterns of association among individual mobility, the built environment, and behavioral outcomes," Kirchner says. The team is now using the same methodology to study the way the growing availability of e-cigarettes in point-of-sale outlets may affect youth and adult decisions to purchase combustible cigarettes.

The public health imperative indicates why it's important to keep studying e-cigarettes in formats like this, says Johns Hopkins's Henningfield.

 "We can't force people to do certain things," Henningfield says. "But we know that we can alter behavior to some degree with communications, regulation and marketing. In this area, like so many others in public health, the outcome will depend very much on behavior at the individual and population levels."

Tori DeAngelis is a writer in Syracuse, N.Y.