Put on a happy face. Let a smile be your umbrella. Turn that frown upside down.

Since childhood, we've been told that if we slap on a smile, happiness will come. And that doesn't just come from your mom trying to make you look more pleasant. The idea that smiling can make you happier and frowning can make you sadder hearkens back to Charles Darwin in the 1800s, NPR points out. Later called "the facial feedback hypothesis," scientists believed that when you change the expression on your face, you can change your mood.

But new research finds that the truth isn't that simple. In a recent paper published in Psychological Bulletin, researchers analyzed the results from 138 studies that tested more than 11,000 participants from all over the world. The data covered more than 50 years of experiments.

After breaking down the studies, they found that smiling does have an impact on emotions — but only a negligible one.

They discovered, for example, that if 100 people smiled — and the circumstances surrounding the smile was the same with all of them — only about seven would likely feel happier than if they hadn't smiled, NPR says.

The researchers also looked into frowning and scowling to see if there was a connection between those forced expressions and feeling angry or mad. In both cases, the connections were small.

"We don't think that people can smile their way to happiness," said lead researcher Nicholas Coles, University of Tennessee Knoxville Ph.D. student in social psychology, in a statement.

"But these findings are exciting because they provide a clue about how the mind and the body interact to shape our conscious experience of emotion. We still have a lot to learn about these facial feedback effects, but this meta-analysis put us a little closer to understanding how emotions work."

History and forced expressions

waiter smiling After a day of smiling at customers, some people in the service industry are more likely to drink in their off hours. (Photo: vectorfusionart/Shutterstock)

The classic smiling/frowning test dates back to 1988 when people were asked to rate how funny cartoons were while holding a pen either between their teeth or their lips. When you hold a pen in your teeth, you'll see that you are somewhat forced to smile. However, when you hold one in your lips, you appear as if you're frowning.

Interestingly, the people who had the pen in their lips rated the cartoons as less funny than those who had the pen in their teeth. But later, many researchers tried to replicate the results and couldn't, writes The Guardian. It wasn't until Israeli researchers re-ran the experiment with and without video cameras in the room that the original results were reproduced. Participants reacted the same way as in the first experiment as long as they weren't being recorded.

More recently, a study published in the Journal of Occupational Health Psychology found that there may be a negative to putting on a happy face when you're not feeling it.

People who have to smile a lot for their jobs — especially in retail and service industry jobs — end up drinking more when they're off the clock.

"Faking and suppressing emotions with customers was related to drinking beyond the stress of the job or feeling negatively," Alicia Grandey, a psychology professor at Penn State, told Penn State News. "It wasn't just feeling badly that makes them reach for a drink. Instead, the more they have to control negative emotions at work, the less they are able to control their alcohol intake after work."

So maybe sometimes, turning that frown upside down isn't such a great idea after all.

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.

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