I think this type of depression that is supposedly a response to social media is simply a symptom of something that would have manifested itself with or without being plugged in.

One might write a novel on the subject, but humans are easily dissatisfied. We chase after things we think we want, but are really unfulfilling. Many of us lack a true calling. We travel to exotic places and buy expensive things only to realize that the hedonistic treadmill is real.