Do selfie's make you happy? Or do happy people take selfies?

I doubt that the selfie was the cause of their increase in happiness. There are so many more factors that this experiement seems to ignore.

(New relationships, finding out what they want to do with their life, achieving success in academics or athletics. All of these are things that are more important to a college student than taking a selfie, and therefore direct a greater change in mood)

I wonder when the study started and ended. Time-of-year means many things. Also, time of day.

Too many variables left unaccounted for. (At least from what I can tell from reading this article.)