Both of your hypotheses, even if rejected, only point to correlated data. Correlation studies, especially those that rely on self-reported surveys, are very, very close to worthless, scientifically. FWIW, I happen to detest almost all social media, even the ones I use, so I don't find the conclusions of the study unbelievable--but it's just that the data they're using aren't what's making me believe it; it's my own experience.
You always need a control if you want to make a point that is believable. And not a historic control--a randomized, prospective control.