A smile, no matter how genuine or unnatural it is, can relieve stress. This has been suggested by an experiment that rounded 169 people together to observe whether smiling has any effect on stress.
The test required participants to use chopsticks to control facial muscles into producing a neutral expression, a standard smile (contained in the muscles surrounding the mouth, and a Duchenne smile (extends to the eyes). There were also some who were instructed to smile, exhibiting a forced type.
Afterwards, they were given a series of multitasking activities that are highly stressful, which proved very strenuous compounded by the fact that they need to hold chopsticks within their mouths. Heart rates and notable stress changes were monitored throughout the entire task.
Results show that those who were told to smile had better recovery from the stress and incurred lower heart rates compared to those told to keep a neutral expression. Furthermore, participants who held a Duchenne smile recovered the best. Interesting enough, people who held fake smiles experienced better relief than the non-smiling group.
This led to the conclusion that smiles — including fake ones — can actually improve stress levels in a person.