In the FT, Leslie Hook reports that activist investors want Apple

to address concerns over smartphone addiction and the mental health effects of phone use among children.

They refer to psychologist Jean Twenge according to whom teenagers today (“the iGen”)

… are more vulnerable than Millennials were: Rates of teen depression and suicide have skyrocketed since 2011. It’s not an exaggeration to describe iGen as being on the brink of the worst mental-health crisis in decades. Much of this deterioration can be traced to their phones. …

12th-graders in 2015 were going out less often than eighth-graders did as recently as 2009. …

Teens who spend more time than average on screen activities are more likely to be unhappy, and those who spend more time than average on nonscreen activities are more likely to be happy. There’s not a single exception. All screen activities are linked to less happiness, and all nonscreen activities are linked to more happiness.

The last observation does not hold in the cross section, however; more “social” teenagers spend more time with friends both online and offline.