I'm of the opinion, and the stats are slowly coming in to back this up, that it's all our mental health, not just youths this is affecting.
Always being "on" leaves us always wired for threat, we never feel safe and secure because any second a news alert says that there has been a terrorist attack, a text message saying something has happened, an email your hind brain worries about being unresolved.
We were not built for this. It's screwing with us on a very core level.
Unfortunately we have built the world in a way where it is near impossible to not have a smart phone and still function - you can barely use a car park or eat in a restaurant without one.
What you can do is turn off ALL the notifications, remove every single piece of social media and news, and have a dedicated period where you go and look at your texts, your emails or whatever if you need to - and preferably on a desktop computer in a specific room.
Putting your smartphone on a shelf, a hardish to get to one, maybe the kitchen, so you don't just pick it up every time you have a mental itch of discomfort, can do huge things for underlying stress levels as well.