School smartphone ban results in better sleep and improved mood: study 2 years ago
For increased happiness it is the ban of addictive websites. Likes, dislikes and most importantly, flagging, censoring and cancelling, externalizes your locus of control and makes you think that you live in a dystopian world.
The Internet wasn't this bad when people were on Usenet and no one would censor your thoughts.
For cognitive abilities it is the phone ban itself.