Proving that Facebook "causes" depression seems like a pretty high bar. Showing that Facebook contributes to or exacerbates an underlying propensity for depress

Proving that Facebook "causes" depression seems like a pretty high bar. Showing that Facebook contributes to or exacerbates an underlying propensity for depression seems to have strong support in the current research. The more interesting question is how does Facebook amplify this as an underlying tendency of social media in general (or even what we euphemistically refer to as "being online")? Who's more depressed, Facebook users or Twitter users? Why is that?