It sounds like the most useless advice imaginable: Just put on a happy face. Conventional wisdom is that smiling is an effect of feeling happy, rather than the other way around. Simply smiling in stressful situations can’t possibly make you feel any better, right?

Wrong. A fascinating new study by University of Kansas psychologists that will soon be published in the journal Psychological Science indicates that, in some circumstances, smiling can actually reduce stress and help us feel better.

“Age old adages, such as ‘grin and bear it,’ have suggested smiling to be not only an important nonverbal indicator of happiness but also wishfully promotes smiling as a panacea for life’s stressful events,” said researcher Tara Kraft. “We wanted to examine whether these adages had scientific merit; whether smiling could have real health-relevant benefits.”

To investigate the claim, the researchers recruited 169 willing college students for a hands-on experiment. But they had to engage in a bit of deception. Actually telling the participants that they were testing whether smiling would make them happier would have distorted the results, so the students were told that the experiment was about multi-tasking.

First, the participants were instructed on how to perform an unusual task: holding chopsticks in their mouths in particular ways that prompted various facial expressions. They were divided into three groups, one that was taught how to form a neutral expression, one that learned how to form a normal smile, and one that was instructed to form a Duchenne smile (also known as a genuine smile), which involves the use of eye muscles, as well as those around the mouth. Additionally, only half of the smilers actually heard the world “smile” during the learning phase; the others were simply taught how to hold the chopsticks in a way that produced smiles, without the expression being identified as such.

Next, the students were put in “multi-tasking situations” that were intentionally designed to be stressful. In the first one, they were asked to trace a star shape with their non-dominant hand while looking only at a mirror image of it, and were misled about the average person’s accuracy in completing the task. While attempting to execute the maneuver with as few errors as possible to win a reward (a chocolate), they were continually reminded to hold the chopsticks in their mouths to maintain the intended facial expression. Afterward, they were instructed to do the same as their hands were submerged in ice water.

During and after each of these tasks, the participants’ heart rates were continuously monitored, and at regular intervals, they were asked to report their levels of stress.

The experiment’s findings were startling. As a whole, the smilers had lower heart rates while recovering from the stressful tasks than those who had assumed neutral expressions, and those with Duchenne smiles had lower heart rates yet. Even those who were smiling only due to their instructed chopstick position—without explicitly being told to smile—showed the same effect. Since heart rate is an indicator of the body’s stress response, it seems as though the act of smiling actually reduced the participants’ overall stress level.

Most intriguingly, a small difference was noted in the self-reported stress levels of the groups after the ice water task. Although the amount of positive feelings declined for all participants after putting their hands in ice water, the decline was slightly smaller for smilers than for those with neutral expressions.

Researchers are baffled regarding why this might happen. The connection between facial expressions and underlying mental states is still largely unexplored, but some have suggested that smiling could reduce levels of cortisol, a stress-related hormone. This study flips our traditional understanding of emotion and appearance on its head: Feeling good could sometimes be a consequence of smiling, not just the other way around.

What does this mean for your daily life? When feeling stressed, try forcing a smile on your face. If you can manage a genuine, Duchenne smile—what people often refer to as “smiling with your eyes,” not just your mouth—that’s even better. For whatever reason, forcing yourself to look happier could actually end up helping you feel happier.

“The next time you are stuck in traffic or are experiencing some other type of stress you might try to hold your face in a smile for a moment,” said Sarah Pressman, one of the researchers. “Not only will it help you ‘grin and bear it’ psychologically, but it might actually help your heart health as well.”