A York University researcher and his student have built a mathematical model to understand how peer influence plays a role in vaping among teenagers, and also in their decision to quit and perhaps start again.
"A lot of people, when they think about math, think about geometry and Pythagoras' theorem," says Iain Moyles, an associate professor in York's Department of Mathematics & Statistics. "Math is a language of structure and logic and science that can help you test a hypothesis. So we've designed a mathematical model to understand the cause and effect of peer influence in smoking."
Iain Moyles
The idea came from PhD student Sarah Machado-Marques in response to a class assignment to experiment with math modelling to explain the psychology behind human behaviour.
Although she has never vaped, she says she wanted to understand why so many of her peers took up the e-cigarette craze when they were in high school.
"I'm really interested in why people do what they do, what drives people to make certain decisions," she says. "I was walking around campus and noticed that vaping is still relevant in both my age group and also younger age groups, and so I started thinking, how can we use math to address this problem?"
Ten years ago, the surge in vaping among adolescents was considered an epidemic. In 2018, the number of U.S. high-school students vaping nearly doubled in a single year, according to the American Heart Association. More recent data, from Statistics Canada, shows that vaping is still popular among Canadian youth. In 2022, one in 10 Canadians aged 20 to 24 and one in 15 aged 15 to 19 vaped every day, compared with one in 50 Canadians aged 25 and older.
Moyles says the vaping epidemic is not a classic disease like COVID-19 but a social contagion that behaves like one.
"In a standard disease, you might walk past someone and infect them with an actual virus or bacteria," he says. "In vaping or similar behaviours, an adolescent can pressure someone and you change your behaviour because you were infected' by the influence of your peer."
Sarah Machado-Marques
Machado-Marques says it can be a subtle pressure, where teenagers and young adults feel the need to fit in or mimic the behaviour of their friends.
What their research suggests is that while teenagers can be influenced to vape because their friends are, equally so, they may be influenced to quit the habit because their friends are. Their mathematical model shows that the long-term trajectory of vaping is a cyclical pattern of starting and quitting depending on what their cohort is doing.
"We see this re-emergence in society all the time - things that were cool when we were kids, then weren't cool," says Moyles. "Our kids and our grandkids eventually find them again and once again they become cool."
The findings from Machado-Marques and Moyles can apply to any adolescent trend where friends have influence on each other. The same cycle can be seen in the pendulum between bell bottoms and skinny jeans, and curly and straight hair, for example.
Moyles says math modelling can be used by parents, teachers and public health authorities to identify cycles of undesirable adolescent behaviours influenced by peers and look for opportunities to intervene.
"The key learning I would say from our modelling would be to recognize the cycle and to start to saying, OK, when do we think this sort of thing is happening and how do we get ahead of it?'"
The researchers say that while prevention is always best, attempts to influence more positive behaviour among adolescents may be strongest coming from other adolescents.
"If a parent or teacher encourages a certain behaviour, adolescents might do the opposite, just because it's not coming from within their influence group," says Moyles. "The key from the influence structure of our model is to find a way to have that information coming through the peer network."
This story was originally featured in YFile, York University's community newsletter.
