While companies are promoting e-cigarettes to young Canadians, researchers do not yet know how nicotine delivered by these vaping devices affects teenagers’ brains.

“We don’t really know very much at all with respect to [nicotine’s impact on] human adolescents,” said Laurie Zawertailo, senior scientist with the Nicotine Dependence Service at Toronto’s Centre for Addiction and Mental Health.

The vast majority of studies on the effects of the drug on developing adolescent brains have been on laboratory rodents, she said. Some of those studies have suggested rats may be more responsive to nicotine during adolescence, but these findings do not necessarily translate to humans.

Story continues below advertisement

In human studies, teens who smoke have been found to be more likely than non-smokers to be impulsive and take risks, and are heavily influenced by their peers, Zawertailo said. Imaging studies on humans have also shown some differences in brain structure and brain activity between adolescent and young adult smokers and their non-smoking counterparts.

But scientists do not know whether any of these are pre-existing differences, or the effects of nicotine exposure. Moreover, the brains of teenage smokers do not appear very different from those of adult smokers, she said.

So while nicotine certainly stimulates the brain’s reward system, it’s unknown whether it affects brain development, she said.

The way in which people administer or consume a drug has an impact on how addictive the drug may be, Zawertailo said. While there is the potential for e-cigarettes to become habit-forming, “by far, smoking is the most addictive,” she said. “That’s the way that nicotine can get to the brain the fastest and with the highest peak.”

Even so, she emphasized the purpose of e-cigarettes is to help smokers stop smoking tobacco.

“If you don’t smoke cigarettes, you shouldn’t vape,” she said.

Although researchers still have many unanswered questions, neuroscientist Huib Mansvelder, head of the department of neurophysiology at Vrije Universiteit in Amsterdam said he worries that e-cigarette companies are targeting teens with various sweet flavours and colourful packaging.

Story continues below advertisement

Over the past two decades, his own research on lab animals has convinced him e-cigarettes should be treated as a controlled medicine, available through pharmacies or doctors and kept far away from teens who have never been exposed to nicotine. Even then, he said he believes they should only be used as a last resort for long-term smokers, who have tried counselling, medicine and nicotine patches or gum.

“That would be the only use of e-cigarettes that I can think of that would make sense,” he said.

Our Morning Update and Evening Update newsletters are written by Globe editors, giving you a concise summary of the day’s most important headlines. Sign up today.