There has been a long standing debate about people saying that it takes a lot more muscles to frown as compared to smile. This is not true that it takes around 48 muscles to frown, it takes a lot less and it is safe to say that the number of muscles taken to frown and to smile are almost similar with just 1 or 2 muscles difference. Frowning is a complex expression of face which involves the movement of multiple facial muscles to bring the movement of the Eyebrows, Eyelids, upper lip, lower lip, chin etc.
What differs from person to person is the way they Frown, there are multiple ways in which people frown and according to some studies it is seen that it depends on gender, race and sometimes people from different locations frown differently. This means that the number of muscles used to frown also differs.
List of Muscles used to Frown:
Frontalis: 2 muscles, Elevate both the eyebrows
Procerus: 1 muscle
Orbicularis Oris: 2 muscles used to close the mouth
Depressor Anguli Oris: 2 muscles draw the angle of the mouth downward
Depressor Labii Inferioris: 2 muscles Lower the Lower lip on both sides
Mentalis: 2 muscles, move the Chin up
Platysma: 2 muscles move the lower lip downwards and backwards
There are multiple studies which are contradicting the use of Procerus muslce and Frontalis muscle to determine the movement of the upper eyelids and forehead. Some studies show that only the Procerus Muscle is used and some mention that Frontalis muscle is used. The number of muscles used to Frown is mentioned as 11, but with the contradicting statements by studies it is not clear to determine the exact number.
If we count only the Procerus muscle without the Frontalis the count goes to 11, if the Frontalis is included without Procerus the count is 12 and if both are included the count goes to 13. So it is safe to say the the exact number of muscles used to frown can be anywhere between 11 to 13.