Yes, yes, and yes again. When you smile, you encourage the use of serotonin which makes us feel good.
You won´t automatically feel happy if you´re sad, but tests have proved that depressed people improve if they smile as often as possible.. Even a forced smile helps.
Give it a try. It certainly won´t make you feel worse. If you can find something to laugh at ..... even better.
Laughter is the best medicine is not a myth.