Most people using TitTok already have a mental disorder called "narcissism". Not so long from now, companies like Instagram, Snapchat, and TikTok would be banned for the impossible to measure but huge damage made to the society. Facebook is also evil, but for many other types of damages. And it's not like these companies don't know what they actually are causing - they perfect know to conditions they put youngster in…
I think you have to break apart those 'using' TikTok by anonymously consuming content, and those who are 'using' TikTok by producing content with the aspiration of hitting it big. Narcissism seems connected to the second, but not so much the first.