The answer of why [social media has a greater negative mental health effect on teenage girls than it does on boys] is quite obvious to many people but no longer politically acceptable.

There is a large external pressure for studies to show that there are no differences between men and women while there is also demand for studies that show negative outcomes of women in comparison to men. The same problem happens again and again with these studies in that nothing explains the negative outcomes of women. Except one explanation that is instantly discarded for being socially untenable.

The intersectionalist looks at the studies and declares, "It must be something - let's keep looking!" while the sexist takes a look and nods.

Nobody is going to risk their careers or their funding when they can continue being paid to investigate other avenues of explanation. The suffering of people will continue until a more acceptable explanation is found.

And because I don't wish to speak between the lines: There are psychological and emotional differences between men and women. And, from all the humans I've known at least, women tend to give more of a shit about the opinions of other people than men give a shit about the opinions of other people. While the toxic negativity of social media impacts both genders I would honestly be shocked if it didn't impact women more if for no reason other than because they care more.