In a tough situation? Slap a smile on and you're body will feel less stress. (Photo: Creative Commons: Flickr/seanb)

The old adage "Just grin and bear it" may have some scientific merit after all. A study forthcoming in the journal Psychological Science shows that a simple smile can trick your body, reverse engineering the lack of stress that a grin usually signifies.

"We wanted to examine whether these adages had scientific merit; whether smiling could have real health-relevant benefits," said researcher Tara Kraft of the University of Kansas, according to Health Canal.

Smiles come in two categories: standard smiles, which engage the muscles around the mouth, and genuine or Duchenne smiles, which use both mouth muscles and those around the eyes. Positive emotions have been shown in previous studies to help in times of stress, but Kraft and her associate Sarah Pressman wanted to test whether manipulating the types of smiles people make could affect the body's response to stress.

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Using 169 participants, Kraft and Pressman split the group into three sections and asked each to group to make a different facial expression. Some were instructed to make a standard smile, others were asked to do a Duchenne smile, and the third group was trained to hold chopsticks in their mouths in such a way that forced them to engage smiling muscles without being instructed to smile.

They were then asked to work on multitasking activities designed to elicit stress. The first required participants to draw a star with their non-dominant hand by looking at a reflection in a mirror. The second had study participants submerging a hand in ice water.

By measuring participants' heart rates and self-reported levels of stress, the researchers found that smiling may actually influence our physical state. Compared to participants who held neutral facial expressions (through the use of chopsticks), participants who were instructed to smile, and in particular those with Duchenne smiles, had lower heart rate levels after recovery from the stressful activities.

The participants who held chopsticks in a manner that forced them to smile also reported a smaller decrease in positive affect compared to those who held neutral facial expressions.

"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 Pressman, according to Live Science. "Not only will it help you 'grin and bear it' psychologically, but it might actually help your heart health as well!"