There is/was some research on this, and the results were that you actually get more depressed because you feel as if your life is dull because when you have an X number of friends(or the twitter following equivalent) you see everyone's top moments, not the downsides. That makes you feel down.
And social media is addictive because it makes use of short dopamine loops.
Both two very interesting things to read up on.
RE: Does social media cause depression ?