Interesting study. Personally, I smile relatively often even when depressed and sometimes it lifts my mood. Not sure I would try Botox since I could maybe achieve the same results with smiling?. This concept reminds me of "half smile" in DBT. Could be something to try out and make an effort to do when I am feeling down.
Turn That Mood Upside Down With the Miraculous HALF-SMILE — Cognitive Behavioral Therapy Los Angeles