Earlier quoted context omitted.
This is a logical fallacy. If you increase the dosage of mercury, it'll eventually be deadly. In the same vein, smart phones, social media, etc are entirely different beasts to books, radio and even television.
And we'll adjust, as we always do. It's fine to have this discussion, but the position that it can "destroy you" and comparing it to a lethal dosage of mercury is on the extreme end of the discussion.
I don't understand this line of thinking. Sure, it may not be the literal end of the world, but that doesn't mean that it won't cause a lot of damage before people 'adapt'. People have always adapted to wars, but that doesn't mean that the world wars weren't absolutely catastrophic.
And while I don't think that smartphones will 'destroy you', I think there's a good chance that it can both be very corrosive in all sorts of manners. I think smartphones are a lot more potent at sedating people and making them detached than novels ever could hope to be, which can have a very harmful impact on society at large.