Depression rates among youth were declining until they began sharply increasing around 2012 when smartphones (with their on-device social media apps) began to become popular.
That's some great correlation, but does not imply causation. The study helps firm up the causal link, but your "makes sense" implies that the causation is intuitive but I don't think it is.
Depression rates among youth were declining until they began sharply increasing around 2012 when smartphones (with their on-device social media apps) began to become popular.