Since teens first took the wheel, studies have examined how drug use and other risky behaviors impact their driving. But what if we looked at that scenario from the other way around? Could it be that driving —and the new independence that comes with it — actually influences the risks that teens take? Gies assistant professor and micro-economist Julian Reif wanted to find out. So, together with former University of Illinois Urbana-Champaign PhD student Jason Huh, he embarked on a study exploring the effect of teenage driving on mortality and risky behaviors.

“We were interested in understanding determinants of risky behaviors among teenagers,” said Reif, whose new paper "Teenage Driving, Mortality, and Risky Behaviors" is forthcoming in the journal American Economic Review: Insights. “From prior research, we know a lot of descriptive facts about their key behaviors. In particular, there are a lot of differences between males and females in terms of the kinds of ways they’re most likely to die.”

Males, for example, are about four more times likely to die by suicide or accident than females, said Reif (right). But he wanted to go beyond those numbers by looking at teen deaths that occur at the time when teens first become eligible to drive.

“We thought it was a good experiment for two reasons,” he said. “One is that gaining a driver’s license can lead to large social changes for teenagers. The other is a statistical reason: driver’s license eligibility depends on the month in which you were born, which is basically random.”

In theory, said Reif, there should be little difference between someone who’s 15 years, 11 months old, and someone who’s just turned 16, except that the 16-year-old is eligible to drive in many states. Comparing teenagers just above the driving eligibility age to those just below it provides a unique opportunity to investigate the effects of teenage driving.

Going into the study, there were a few things they expected to find, like an increase in car-related fatalities as teens transition from being passengers to taking the wheel. Sadly for anxious parents, those assumptions were borne out in the numbers.  In the first month that teenagers become eligible to drive, the study revealed that motor vehicle fatalities increase by 44%.

They also discovered a stark rise in the number of females dying from poisoning, which has a far less obvious link. “There are two main ways you can die from poisoning,” explained Reif. “One is a drug overdose; the other is carbon monoxide poisoning. Our study found a sudden and substantial increase in both types of death in the month that teenagers become eligible to drive.”

How substantial? As high as 76%, said Reif. “If you look at the graph, it’s an unmistakable increase.” What makes that statistic even more remarkable, however, is the clear gender divide. “When we look at teenage males, we find no effect at all.”

So what’s behind this anomaly? Without additional research, it’s hard to say. It could be that driving enables female teenagers to purchase and consume drugs more easily, or that it alters their social environment, allowing them to meet new friends who may influence their decisions. Ultimately, that will be up for future researchers to investigate. The important thing is understanding that there may be a causal link.

“Male and female teenagers exhibit very different risky behaviors,” said Reif. “We’re not the first ones to point this out, but nobody has been able to find out the causal forces behind these differences. We show that driving is one of those forces. When teenagers become eligible to drive, that event is causing an effect in females that is not happening in males.”

While this study doesn’t explain the whole divide, it reveals one small piece of the puzzle, and Reif hopes that’s enough to spark additional research that could lead to solutions in the future. “The more we understand the forces and mechanisms behind preventable teenage deaths, the more we can design better policies that help address them.”