|Smiling is my favorite thing!|
Studies at the University of Michigan, University of Kansas, and an independent clinical study arrived at similar conclusions using three different methodologies.
In the most comprehensive study at the University of Kansas in 2012, 169 people were assigned one of three different facial expressions; a neutral expression, a typical mild smile, or an extreme smile lifting the cheeks known as a Duchenne smile. Then researchers used chopsticks to physically hold the expression in place. Participants were then asked to do a series of multitasking tasks, some of them quite stressful.
When asked about their mood and emotional state, the participants forced to smile were dramatically less stressed and happier.
It's quite possible that the physical act of smiling, as well as the extremes to which you smile, can have a psychological effect on your mood and your ability to manage stressful tasks.