Early social media use in grade 6 harms Italian and math performance over the school career

A longitudinal study of 5,227 Italian students finds that opening a personal social media profile in grades 6–8 leads to negative, lasting declines in Italian and mathematics competence by grade 8 and persists to grade 10, while English remains unaffected. The adverse effects are larger with earlier exposure and are partially mediated by smartphone pervasiveness, which explains a substantial portion of the harm. Using a difference-in-differences design with careful matching and robustness checks, the authors argue the effects are causal within this context, though generalizability and potential unobserved confounding are acknowledged.