According to the media hysteria of any given moment, teens are always inundated with one new threat after another, and maybe they sometimes even really are, but they deserve a bit of credit for resilience, and in any case i'd call this one fairly mild in comparison to historical dangers.
Compared to past worries like military conscription (often deadly), mass state propaganda, and the crazy political cultures of decades past, the threat today from phones to teenagers is pretty tame and even gives them easy access to real information and data so much better than the past allowed for hammering down nonsense ideas and dishonest, manipulative claims. These latter two things have always been thrown at kids, today they finally have immediately accessible tools for digging deeper like never in human history.
Also, for when phones really do get tedious with an overload of corporate marketing and promotion garbage (Thanks so many of you high-paid BigTech/AdTech workers later commenting against online BigTech advertising right here on this very site!), you see, all modern devices have these little physical and digital buttons that let you set parameters to their behavior. Unbelievable as it seems, by pressing them in certain ways, it's possible to mute all sorts of notifications and prompts. My phone is right beside me all day, silent and discreet as an English butler unless I actively open it and seek sometimes, all because i set it to shut the fuck up with just a few moments of touch and clicking around. Any teen can usually do the same just as easily.
I know that many on HN will blather on about "disinformation", teen self esteem through social media and so forth as modern phone-related risks. However, much of this too is exaggerated or describes dangers lighter than the youth isolation of the past, which kids before mass digital communication had far fewer avenues for escaping from through access to their own personal interests and circles online.
If one thing truly is a danger to teens in modern phones and digital communications via social media spheres, its not so much too many notifications as it is the normalization of total 24-hour surveillance by faceless entities "serving your interests" and the inevitable data collection that makes young indiscretions now ever more literally unforgettable in the worst sense of the word.