Seeing people use electronic cigarettes may increase the urge to smoke among young tobacco users, according to a recent study.

Researchers from the University of Chicago Medical Center found that the elevated desire to light up associated with seeing people smoke e-cigarettes is as strong as when observing someone smoking a regular cigarette.

The electronic devices deliver nicotine via a heated solution of compounds and flavorings. The vapor is inhaled by users and closely resembles the smoke released by combustible cigarettes. Researchers have looked at the health effects of e-cigarette vapor, but no studies have been conducted on the visual effects of e-cigarette use.

"E-cigarette use has increased dramatically over the past few years, so observations and passive exposure will no doubt increase as well," Andrea King, study author and professor of psychiatry and behavioral neuroscience at the University of Chicago, said in a statement. "It's important to note that there could be effects of being in the company of an e-cigarette user, particularly for young smokers. For example, it's possible that seeing e-cigarette use may promote more smoking behavior and less quitting."

For the study, researchers recruited 60 young adult smokers. Participants in the study were told they were being tested on their responses to a variety of social interactions. They were paired with an actor, pretending to be a participant, who would smoke an e-cigarette or a regular cigarette during a conversation. The actual study subjects were measured for their urge to smoke at multiple points before and after this interaction.

The research team found that seeing e-cigarette use significantly increased the observer's desire to smoke both regular and e-cigarettes. The increases in desire to smoke a regular cigarette after observing e-cigarette use were as strong as after observing regular cigarette use.

Researchers said observing regular cigarette use did not increase participants' desire to smoke an e-cigarette.

"Whether participants were exposed to someone smoking a combustible or an e-cigarette, the urge to smoke a combustible cigarette was just as high in either condition," King said. "We know from past research that seeing regular cigarette use is a potent cue for someone to want to smoke. We did not know if seeing e-cigarette use would produce the same effect. But that is exactly what we found. When we re-tested participants 20 minutes after exposure, the desire to smoke remained elevated."

The study is the first to investigate the behavioral effects of exposure to e-cigarette use in a controlled setting.

"This study was our first investigation, and there are still many unanswered questions. We don't know about the effects on a non-smoker or a person who has quit smoking or if responses are different for the various e-cigarette brands," King said. "But if the results do generalize and we show this in other groups, it's important to consider policy going forward in terms of reducing harm for both users and observers of e-cigarettes."

The findings were recently published in the journal Tobacco Control.