THAT'S THE WHY:THE WORK deadlines are stacking up like a losing game of Tetris. Your toddler has just tipped a plate of food into your lap in a restaurant. You're late for an important meeting but you are stuck in traffic.

Grin and bear it, the saying goes. And a new study backs up the notion that forcing a smile can be a help.

The research, at the University of Kansas, asked 170 people to hold chopsticks in their mouths as they carried out stressful tasks – one had them tracing a star with their non- dominant hand by looking at a reflection of the star in a mirror, the other putting a hand in ice water.

Depending on how the participants held the chopsticks as they carried out the tasks, they made a “Duchenne” smile that engaged muscles around the mouth and eyes, a smile that engaged just the muscles around the mouth or they adopted a neutral expression.

On top of that, some volunteers were asked to smile during tasks while others were not given any instruction to smile.

“Findings revealed that all smiling participants, regardless of whether they were aware of smiling, had lower heart rates during stress recovery than the neutral group, with a slight advantage for those with Duchenne smiles,” write the authors in the journal Psychological Science.

So next time you feel the tension rising, maybe try smiling, even if you don’t feel like it.