When girls started spending hours each day on Instagram, they lost many of the benefits of play. (Boys lost less, and may even have gained, when they took up multiplayer fantasy games, especially those that put them into teams.) The wrong photo can lead to school-wide or even national infamy, cyberbullying from strangers, and a permanent scarlet letter. Performative social media also puts girls into a trap: Those who choose not to play the game are cut off from their classmates. Instagram and more recently TikTok have become wired into the way teens interact, much as the telephone became essential to past generations.

Facebook’s researchers understand the implications of this rewiring. In one slide from an internal presentation on Instagram’s mental-health effects, the presenter notes that “parents can’t understand and don’t know how to help.” The slide explains: “Today’s parents came of age in a time before smartphones and social media, but social media has fundamentally changed the landscape of adolescence.”

Social-media platforms were not initially designed for children, but children have nevertheless been the subject of a gigantic national experiment testing the effects of those platforms. Without a proper control group, we can’t be certain that the experiment has been a catastrophic failure, but it probably has been. Until someone comes up with a more plausible explanation for what has happened to Gen Z girls, the most prudent course of action for regulators, legislators, and parents is to take steps to mitigate the harm. Here are three: