[jarofgreen]

> Unless they're missing some other factor

From Abstract: "and a comprehensive set of potential 3rd variables were included as covariates in each analysis".

Sounds like they certainly tried to control for that - you'd have to read the full study to see the details.

[gojomo]

Yes, too bad the full text is behind a paywall. So I haven't read the full study, but I was once upon a time a teenager.

I recall many aspects of my and my peer's psychological lives that would not be easily available to an outside researcher as part of their "comprehensive set of potential 3rd variables".