Sarah Pressman, assistant professor of psychology & social behavior at UC Irvine, and her dog, Milo, enjoy an afternoon at William R. Mason Regional Park near campus. She studies the link between happiness and health. Steve Zylius / UC Irvine

Driving on the 405 freeway in Orange County rush-hour traffic, Sarah Pressman can be forgiven if she doesn’t feel like smiling. When other cars cut her off or ride her bumper, she’s tempted to do what many commuters do: curse or engage in some creative sign language. But she grins and bears it – even if it means clamping a pen between her teeth to force herself to smile.

“I literally put a pen in my mouth when I drive. It helps because you can’t feel really angry and stressed when you have this ridiculous smile on your face,” Pressman says.

She takes smiling seriously – and for good reason. An assistant professor of psychology & social behavior at UC Irvine, she studies the link between positive emotion and physical well-being. Pressman is among the first researchers to demonstrate that happy, optimistic, cheerful people tend to be healthier than those who are sad, angry or depressed, and she’s working to understand why.

“I’m not really studying what makes people happy or how they can improve their life satisfaction,” she says. “I’m trying to understand why people who are happy do better physically. Why do they live longer? Why are they less likely to get cancer? How do these positive traits protect people and keep them healthy, and how can we take advantage of them to help others?”

Put on a happy face

Pressman herself smiles often – a big, natural grin – and speaks fast, as though in a hurry to get to the bottom of her latest query. She’s led a host of studies that delve into the relationship between positive emotion and health. In particular, she’s found that smiles – even the fake, beauty pageant kind – can have beneficial physiological effects, such as lowering blood pressure and reducing pain.

Her research is based on the facial feedback hypothesis, an idea once floated by Charles Darwin that “the simulation of an emotion tends to arouse it in our minds.” Pressman was particularly intrigued by a 1988 German study in which subjects viewed “The Far Side” comics, some while clenching a pen between their teeth to create an automatic smile and others while holding a pen between their puckered lips, as if sipping a straw, to maintain a neutral expression. The smiling group rated the comics funnier than did the neutral group, indicating that any smile, genuine or artificially induced, can lift one’s spirits.

To find out if those happy feelings translate into health benefits, Pressman conducted a study two years ago in which students from a Midwestern university used chopsticks – a more appetizing choice than pens – to maintain either a neutral, nonsmiling expression or a standard, do-you-want-fries-with-that smile. She also coached a third group to practice more natural, ear-to-ear grins – known as Duchenne smiles – that engage the eyes as well as the mouth. Pressman then asked all of them to perform stress-inducing tasks, such as tracing a star with their nondominant hand or submerging their hand in ice water.

Surprisingly, both smiling groups experienced less stress and discomfort than the neutral group. In fact, fake smiles produced nearly the same positive results as real ones. There also were measurable physiological differences. Heart rates of the smiling participants were lower than those of the nonsmilers during the test and dropped faster when it was over.

That something as simple as a smile could have such a profound effect on health garnered a storm of media attention. Pressman’s findings were touted in major outlets such as The Wall Street Journal and The New York Times and even raised smiles among viewers of“ The Colbert Report.” Comedian Stephen Colbert mugged on camera with a pen in his mouth. (Watch the CBS News story “Grin and Bear It” online at

All joking aside, the study has serious health implications.

“When your heart doesn’t go back down to baseline after a stressor’s over, it puts pressure on you. It puts a burden on your heart,” Pressman notes. Individuals whose heart rates remain elevated after stress are more susceptible to future hypertension and heart disease.

Taking the sting out of vaccinations

In a related study, Pressman found that people who smiled while getting a simulated flu shot rated the experience 40 percent less painful than did those who didn’t wear a happy face.

“They also had lower heart rate responses to the stressful experience of the needle,” she says. “I like having physiological data to go along with [the self-reported feedback] because you can’t fake it.”

Seeing potential benefits to children’s health, Pressman is applying for a pediatric grant to conduct a follow-up study.

“I feel we’ll be able to translate this into the real world quite nicely,” she says. “If you can reduce the pain of a flu shot, it might encourage more parents to get their kids vaccinated.” In addition, she and other researchers have shown that vaccines aren’t as effective if people are stressed out while getting their shot; smiling while enduring the needle might offer better protection against the flu.

There are, however, limits to the power of facial expressions over feelings, Pressman notes.

“It’s not going to help people who have chronic stress or chronic pain. If an earthquake happens or a tornado strikes, you’re not going to be able to smile your way out of it,” she says. “But for most of us, the stressors we face day to day are minor, like getting stuck in traffic or stubbing your toe. And these simple interventions seem to be pretty helpful for this kind of thing.”

First-world problem?

Pressman wondered if positive emotions only affected people’s health in developed countries, where “they have the luxury of worrying about their happiness.”

“The question we had was, ‘Would happiness have the same benefits in places where people face famine, homelessness and death due to lack of medical care?’” she says. “We anticipated that it wouldn’t, because there are more pressing things that might impact their health.”

In a first-of-its-kind study involving 142 countries, Pressman used data from the Gallup World Poll to compare participants’ emotional state (the surveys asked if they had recently experienced happiness, enjoyment, worry, sadness, stress, anger, etc.) with their self-reported physical health.

The results surprised her. Emotions actually had a greater influence on health in developing countries such as Sierra Leone and Nigeria than in industrialized nations. For instance, people in Malawi, which has a per capita gross domestic product of $900, show a stronger connection between happiness and wellness than residents of the U.S., with a per capita GDP of $49,800.

One explanation for the finding: People in developed countries have access to medical care that can counteract the effects of negative emotions on the body. “An American with hypertension can take blood pressure-lowering medication. A Malawian cannot,” Pressman says.

Reason to smile

Pressman is now trying to pinpoint which specific positive emotions work best to counteract high blood pressure and cortisol levels, which rise during stress and suppress one’s immune system.

“We want to take a magnifying glass to this and find out which are the most beneficial– feeling calm and relaxed? Vigorous? Excited? Enthusiastic?” she says. So far, her research indicates that an enthusiastic, robust attitude may do the body the most good.

Ultimately, Pressman hopes her work will help people cope better with traffic jams and other stressors of modern life.

“In the U.S., we wear our stress as a badge of honor. People continue to overtax themselves, to put in long hours and have a poor work-life balance,” she says. “We know stress is one of the things killing us. I don’t think it’s going away. So if we could teach people simple strategies to prevent stress from hurting their bodies, that would be fantastic.”