Not JUST correlated with poverty, but likely to a large degree, I agree. Ideally, kids would get a maximum amount of quality time with their parents or siblings instead of being parented by the internet. Wealthier parents parents, I suppose, would be more likely to have the free time (or that of paid help), emotional availability, educated tendancy to read and develop and understand of the importance and structure of shared time, healthy established family norms, and genes. There's a lot going against poor families, and it's not getting easier.

Yes, money is also a factor. You can see some data in https://substack.com/home/post/p-140838494 by the same guys.

I am pretty well off and I am very guilty of letting my kids overuse electronics. Plenty of my friends are the same (we've discussed it).

The school my son used to attend wanted to be hi tech (I guess) and gave all kids iPads with all textbooks and assignments provided this way. You don't need a study or aversion to technology to realize how bad they are for this purpose. The screen is small, constrained and low fidelity compared to a paper text book. It also (by default, as provisioned) turns off every ~5s to save battery life which is incredibly annoying. It is just objectively worse than paper.

Content on TV (for better or worse) is regulated, and those regulations are periodically updated to address the moral outrage of the day.

That is a fair point. I was asking whether the cause was bad parenting and not smart phones itself. The mental health issues reference was pointless and makes no sense.

The confounding variables they are aware of, you mean. The problem is the confounding variables they aren’t aware of.