Facial muscles express emotion but are also involved in how you experience your emotions. By this I mean that your facial muscle actions affect your mood and perception.
It is thought that the lack of positive facial muscle feedback means that a positive mood is harder to maintain.
For example, there is mounting evidence and studies to show that patients who are unable to smile suffer from more depression.
So how can we use that positively?
One study looked at the treatment of botulinum toxin for glabellar frown lines, which involved injections into the corrugated (frown) muscle, paralysing them for up to 6 months. The cosmetic effect of this treatment is a smoother forehead and no frown.
This results in a significantly more positive mood than those who had not had treatment, and was measured by anxiety and depression scores.
Frowning is associated with sadness, anger, fear, distress and pain. By paralysing the corrugator muscle, it makes it impossible to perform negative facial expressions, and so negative mood is harder to maintain. The lack of negative mood feedback from the facial muscles actually leads people to feel happier.
Furthermore, facial expressions are key in communication with others – with a smoother forehead and no frown, the treatment could potentially have effects on how others perceive you.
This psychological consequence still requires further investigation.
For further information read Michael B Lewis and Patrick J Bowler. Botulinum toxin cosmetic therapy correlates with a more positive mood. Journal of Cosmetic Dermatology. 2009 (8): 24 – 26.