I was surprised to see how closely happiness maps to non-phone activities, and unhappiness maps to phone-related activities.

The author notes that this is a study of correlation, not causation. When I went through moody phases as a teen, I wrote, or worked, or did theater, or church youth group activities.  When I was busy, I had less time to write. When I didn’t feel like going out, and chose to stay home, or for whatever reason had fewer opportunities to go out, I wrote more. The writing didn’t make me depressed, it was just something I did more frequently whenever I spent more time at home.

Likewise, the study doesn’t say that using phones causes teens to be unhappy, just that unhappiness and phone use are correlated.

The pattern is again clear: Nearly all phone activities are linked to less happiness, and nearly all non-phone activities are linked to more happiness. There are two exceptions, both correlations |.01| or under: TV (sometimes non-phone, sometimes phone) is linked to slightly less happiness, and working at a paid job (usually non-phone) does not correlate with happiness (r = .00). An activity not involving phones but that involves screens, video arcades, correlates .03 with happiness (though I’m not sure most teens even know what a video arcade is anymore, and going to an arcade is usually a social activity).

Take a look at the bottom of the chart: Listening to music shows the strongest correlation with unhappiness. That may seem strange at first, but consider how most teens listen to music these days: On their phones, with earbuds firmly in place. Although listening to music is not screen time per se, it is a phone activity for the vast majority of teens. Teens who spend hours listening to music are often shutting out the world, effectively isolating themselves in a cocoon of sound. —Psychology Today