While I don't doubt that social media can have a negative impact on teens... my own experience as the parent of a teen is slightly different and doesn't point to social media as being a driver. At least in my case.
I have a teenager that struggles with anxiety, low self-esteem and depression. He's incredibly smart and is an honors student in high school. BUT he also thinks he's terrible and he's incapable of accepting a compliment or congratulations on a good grade or work which he immediately deflects and says he was lucky or he's not really smart or something negative.
What does this have to do with the article as far as my experience? He's not on social media. While he might consume some social media (ex. TikTok) he doesn't have his own social media accounts. He doesn't have a Facebook account, Instagram account, etc. Which might sound hard to believe and you are likely thinking "I bet he has burner accounts..." but actually he doesn't.
He didn't have a smartphone until he was 13. And while he used an iPad before that it was primarily for playing games and watching Youtube.
What he is into is online gaming and Youtube. I guess you could count Youtube as a form of social media but even with that he's a consumer of the content and not a creator or commenter. So he's not posting videos on Youtube or getting into arguments with people in the Youtube comments, etc. He simply watches content.
So I'm only a sample size of one but I deal with a teen who struggles with a lot of what is described in this article... yet it isn't being driven by social media.
I think there are far more factors at play than simply smartphones and social media. And those factors could be different depending on the individual. Although some of the factors are obviously going to be shared. And I have no doubt social media can have a tremendous negative impact on mental health. But I think there is much more going on than just that.