I suffer from pretty severe depression and when it flares up it can cripple me, so I know a thing or two about mental health. That being said, if Facebook can make you feel inadequate then frankly you need taking out the back and shooting, or maybe just grow up.
Social Media Depression is not a thing. It sounds more like one aspect of a much larger issue called "being vapid and giving too much of a <mod edit> about what other people are doing" perpetuated by tabloid bullshit and celebrity sensationalism. Get your own life first and suddenly what other people do won't affect you.