Yes, as we all know, smiling releases "feel-good" chemicals.
The feel good neurotransmitters dopamine, endorphins and serotonin are
all released when a smile flashes across your face as well. This
not only relaxes your body, but it can lower your heart rate and blood
However, since the 70's, experiments involving forcing subjects to smile and measuring the results have shown us that just the stimulation of the muscles used to smile causes this effect.
“The researchers say their findings suggest smiling during brief
periods of stress may help reduce the body's stress response,
regardless of whether the person actually feels happy or not.”
As such, even a faked smile can make you happier.