"Psychology lecturer John Shaw, who headed up the study, said children were supposed to sleep for between nine to 11 hours a night, per NHS guidelines, but those surveyed reported sleeping an average of 8.7 hours nightly."
So he's comparing what they are "supposed" to sleep with what they actually sleep?
Why not compare actual sleep patterns before social media with those currently, rather than some arbitrary selected measure of what something is "supposed" to be.
Hell I am supposed to be 6 foot, build like Adonis, with more money than Elon Musk. Unfortunately, what I'm "supposed" to be, and what I actually am, are worlds apart. I don't get to claim I "lost height" or "lost muscle" or "lost money".