I read that paragraph and it does not say that facebook causes depression, it says that the relationships between lower well-being and facebook use is dynamic. We can't tell from that whether high facebook use puts a person without other indicators of depression at higher risk of depression or whether it's just that facebook and depression are a self-reinforcing spiral.
But also, that title on the linked article is very misleading. A link between facebook use and depression in the general population does not mean that if you use facebook, you will feel worse. Though, to be fair to the study, that might be like how if you smoke, you might not get lung cancer. I don't see the correlation being that strong, though.