(overseas compared to what? /genq)
i'd say much of the mental illness discourse stems from the fact that these online spaces are most often filled with 14-16 year old kids whose personalities and brains are rapidly developing which can be rather jarring to experience. added on top of this, they're part of a generation who's had access to unlimited information since birth by means of the internet, which makes it painfully easy to misdiagnose yourself with a mental illness.
i was a victim of this pitfall too ~4 years ago, so i can say with certainty that although there's undeniably a larger concentration of mentally ill people around here, a lot of them are just developing teenagers who haven't gotten differential diagnosis.
(in particular i misdiagnosed myself with adhd, which turned out to be a massive dead-end, and only through attending therapy with professionals was i able to be diagnosed with ocd, the actual root of my problems. if i hadn't known i don't have adhd, i might have had a very very different outlook on life.)
sorry about the first part, i was in the middle of a conversation with someone else while typing, gah... i was trying to make a point but i lost track. it was something about how a lot of diagnoses would usually happen in countries where going to a psych + getting a diagnosis is easy and not frowned upon, so the percentage that's presented isn't fully accurate with how many people may actually have it globally.
and yes! i really do agree with your points. with how information spreads online and how difficult it is to know which is true or not, it is painfully easy to be mistaken. however, i do think it has other factors... seeing as many of them are struggling with something, but it's likely they don't have any other outlet or proper support other than the internet. they try to figure out what's wrong by themselves, or whatever other possibility...