When you were a kid you may have been told that it takes fewer muscles to smile than it does to frown. Though it’s a nice sentiment, this isn't strictly true. The mechanics behind smiling and frowning muscles are a little more complicated than that.
The interconnectedness of human facial muscles really makes it difficult (if not outright impossible) to determine exactly how many muscles are used when smiling or frowning. It is known that smiling generally exercises the upper cheek and eye area more, while frowning is usually situated more around the lower mouth and chin. There are many mutual muscles that are used throughout both smiling and frowning, and the amount of effort that is used when doing so generally relates to the severity of the expression rather than the expression itself. In general, most people report that the effort related to smiling or frowning tends to feel related to whether or not they are truly experiencing that emotion. In other words, forcing an expression can feel like more work, regardless of the expression. But that doesn't mean that there aren't some significant differences between the two.
Smiling tends to create smile lines (around the corners of the mouth) and laugh lines (around the corners of the eye). Meanwhile, frowning tends to create wrinkles between the eyes and at the edges of the mouth, in a down-turned angle. Thus, those who smile more frequently and those who frown more frequently may very well have their expressions etched permanently across their face with time -- and that's not all. Psychological studies have often found that those who smile will also begin to feel happier, even if there are no other changes to their situation or environment. Those who smile also seem more approachable and contribute to the happiness of those around them. Thus, a bright, gleaming smile is something that improves the lives of both its owner and those they care about.
Though smiling may not necessarily take fewer muscles than frowning, smiling still takes less of a toll on your body and your mental health. There are many physical and psychological benefits to smiling. Smiling elevates your mood, decreases your stress muscles, relaxes those around you, and even makes you more attractive to others! Brighten someone’s day by flashing your pearly whites!