In this TEDxtalk (transcript is here), the speaker claims that there is a growing amount of research that shows that spending large amounts of time on social media permanently damages the capability of the brain to concentrate:
We have a growing amount of research which tells us that if you spend large portions of your day in a state of fragmented attention, so large portions of your day we are constantly breaking up your attention to get a quick glance, just check and just quickly look at Instagram that this can permanently reduce your capacity for concentration. In other words, you could permanently reduce your capacity to do exactly the type of deep effort that we’re finding to be more and more necessary in an increasingly competitive economy.
Has this indeed been demonstrated scientifically? I could not find any such research.
A possibly related but different question here.