USC study finds that stressed older drivers are three times more likely to brake than calm drivers

November 4, 2008

Life can be stressful, whether you’re an individual watching the stock market crash or a commuter stuck in traffic.

A forthcoming USC study in the journal Psychological Science examines how stress affects decision-making and finds that older adults alter their behavior more than young adults when under stress—particularly in situations involving risk.

“People haven’t looked at how stress affects decision-making, even though so many of our decisions are made under stress,” explains Mara Mather, Ph.D., associate professor of gerontology and psychology at the USC Davis School of Gerontology and lead author of the study. “There’s very little information about this whole topic, and, when you get to age differences, there’s even less.”

Mather and her colleagues Marissa Gorlick, of the USC Emotion and Cognition Lab, and USC doctoral student Nichole Kryla-Lighthall exposed young adults (18 to 33) and older adults (65 to 89) to a stressful event, in this case, holding a hand in ice-cold water for three minutes.

Participants then were asked to play a driving game correlating to a real-life situation in which taking a small amount of risk is common: whether to go for it on a yellow light. Participants started at a green light, were awarded points for every second spent driving during a yellow light, but lost all points if the light turned red while driving. The length of time for the yellow lights was determined randomly.

In other words, Mather said, participants had to decide to take some risk—driving during a yellow light—to score any points at all.

“This is the way life is, quite often. To make more money in your investments, you have to take risk. To end up dating someone, you have to take the risk of going up and saying hello,” Mather says. “When there’s a potential payoff, most of the time you have to take some risk.”

In the control group, which was not exposed to ice-cold water, older adults were actually better drivers than younger adults, the researchers found, scoring higher on the game.

However, in the stressed group, older adults were not only more cautious but were also jerkier drivers, braking and restarting almost three times as much as their calmer peers.

The differences in the effects of stress were consistent even when the researchers accounted for gender, level of education, mood and health self-ratings.

“The everyday commute can be stressful: Someone cuts you off, you’re late already. Are you more likely to try and take a risk than if you weren’t stressed out?” Mather asked. “Our results indicate that stress changes older adults’ strategies.”

The exposure to ice-cold water caused a rise in levels of the hormone cortisol, measured in saliva. Cortisol levels increased significantly among stressed younger and older adults, but did not change significantly from pretest levels for the control group, which was not exposed to ice-cold water.

As Mather explains: “The brain regions that are involved in and activated by stress overlap quite a lot with the brain regions that are involved in decision-making and, in particular, in decisions about risk.”

Signs that you might be stressed behind the wheel include increased irritability, decreased patience and tolerance, and a feeling of tension in your body, such as tight shoulders or a firmer grip on the steering wheel than usual, says Andrea Bardack, L.C.S.W., an employee assistance professional at USC’s Center for Work and Family Life.

She also points to negative thoughts and feeling out of control as indicators of driving anxiety.

Drivers need to recognize their stressors and triggers and decide if they have control over altering the situation, or if it would be more beneficial to just accept it,” says Bardack. “Stress is created by feeling out of control, so figure out what you can do to feel more in control.”

For example, if you are in gridlock, there’s not much you can do, she points out. Instead of getting worked up about a situation you cannot change, Bardack suggests deep breathing or other activities that calm you.

“When dealing with stress, do things that are positive to alleviate symptoms in the moment,” she says. Bardack also recommends looking at the big picture and making lifestyle adjustments that will help you feel less stressed in general.

“Start an exercise routine or something that will help get stress out, and you may be less likely to react negatively when on the road,” she says.