Social media and teenage mental health.

Estimates indicate high-speed wireless internet significantly increased teen girls’ severe mental health diagnoses – by 90% – relative to teen boys over the period when visual social media became dominant in teenage internet use. I find similar effects across all subgroups. When applying the same strategy, I find null impacts for placebo health conditions – ones through which there is no clear channel for social media to operate. The evidence points to adverse effects of visual social media, in light of large gender gaps in visual social media use and documented risks. In turn, the analysis calls attention to policy interventions that could mitigate the harm to young people due to their online activities.