It's plausible that the former variable is "stealing" some of the statistical significance of the latter, leaving the researchers with the impression that the latter is irrelevant.
If you have two independent variables that are highly correlated, and you include both into the model, it's going to be pretty arbitrary which one ends up with statistical significance.
If we're dealing with weak effects and small data, there's very little one can do. That's why epidemiological studies like this kinda suck.
When that's what your data looks like, proper study design either involves testing that hypothesis, or staying the fuck away from making conclusions that take one of those as significant and one as non-significant.
> find no evidence that trends in young adults’ economic circumstances
I... uh... can’t make sense of these two statements together, both of which seem quoted from the paper.
It might be that society is changing as a whole, and that individual variations of internet use don't contain any relevant information.
They found that higher sexual activity correlated with greater levels of depression, especially in men. Sexually active women also correlated with decreases in mental health, but the authors' interpretation was that that decline primarily stems from higher rates of victimization among that population, which would obviously lead to negative mental outcomes.
[0]: https://link.springer.com/content/pdf/10.1007/s10508-019-014...
So I think the focus is about what forces were not present in previous generations, and the Internet is certainly the most conspicuous factor. I'm not saying it's the decisive factor, but I'm not surprised it's a prime culprit.
Note that in many countries, teenagers owning cars (and related activities) are not as prevalent as in the US. When I was a teenager, almost nobody I knew owned a car, and we all used public transportation, so there was no (dating) car culture around this.
Like I said, other countries don't have the same car-centric culture of the US. We've been managing to successfully have sex -- and find sex interesting -- without such an early access to cars!
Where you would have had it, if you lived alone, you wont bother overcoming the "more challenging to find a private space" situation.
Really? If there's anything Game of Thrones kept reminding us of, its that males find defeating/killing other men in battle (and the "in battle" part is important, human warfare is very ritualistic just like Chimpanzee warfare) and fucking women equivocal if not related activities. Our ape brains don't appear to make much difference between virtual and physical, at least not enough to make one a lot less addictive than the other.
I think in a century we're going to be looked upon as barbarians by our ancestors for some of the things we did to our bodies, just as we look upon the earlier generations who leaded gasoline, or smoked pervasively.