The harm is from designing them to be addictive. Anything intentionally designed to be addictive is harmful. You’re basically hacking people’s brains by exploiting failure modes of the dopamine system.
If I remember correctly, other research has shown that it's not just the addictive piece. The social comparison piece is a big cause, especially for teenagers. This means Instagram, for example, which is highly visual and includes friends and friends-of-fiends, would have a worse effect than, say, Reddit.
I think there’s a difference between something just being a bit addicting and scientifically optimizing something to be addicting. Differences in magnitude do matter because there are thresholds in almost everything where a thing becomes harmful.
Coca leaves can be chewed as a stimulant and it’s relatively harmless, though a bit addictive. Extract cocaine and snort it and it’s a lot more addictive. Turn it into freebase crack and it hits even harder and is even more addictive.
If this is coca leaves, Twitter is cocaine and TikTok is crack.
