Chicken or egg with screen time and problems?

What I can't see in this article Screen time linked to psychological problems in children is a clear sign that the alternative hypothesis has been considered: "The results showed that more than two hours per day of both television viewing and recreational computer use were related to higher psychological difficulty scores,"

This led to the statement that restricting children's screen time might be good for them. But what if the relationship between screen-time and psychological disturbance is not cause and effect but effect and cause? Or even both signs of some other (unnoticed or unconsidered) factor that effects both of those things?

Admittedly, I'm being a bit skeptical of things that look like they could feed the 'woe woe and thrice woe' attitude to ICTs, so maybe the interpretation is right. But even if it is, then the cause needs to be known and possibly the question asked whether there are carry-overs or implications for people who have to work with ICTs for 8 or more hours a day ... ? So, my verdict: more research needed ...

PS just found a comment on this research here at Neuranthropology: A way down on the page under 'Digital'; "My guess is that screen time can be a proxy for other things going on in a home, such as parental neglect, and so the real cause of the later psychological problems is not elucidated by this study."