It's hard to control for mere provision of social media access. Eg., if you're supposed to be out in the field all day, when are you mean to access social media?

Social media is, in that case, a replacement activity.

The question, which is i think unanswered, is whether and what its replacing in the lives of children. It may turn out to be: not much. That when taken away, children don't suddenly get more time, attention, socialisation, etc. instead, they just get less. Or that the kinds of tech hellholes theyre dumped in have purely passive interaction, eg., ipad kids.

Actually, there is historical precedent for that: Gen X.

The defining feature of Generation X is the latch-key kid population. Children arriving home to empty houses for hours after school without any kind of social interaction whether in person or online. This would be before the internet, so there was no online social activity. This behavior may have applied to as many as 30-35 million US households where for the first time in US history both parents were expected to work full time outside the house. These children had to learn to entertain themselves, do their own chores, and possibly prepare their own meals. Imagine an entire massive population learning to become largely fully self-sufficient, from an emotional development perspective, as children. They had no substitute solution or alternative activity.