Shift from screen‑time to vulnerability

Large longitudinal null results show that simple 'hours‑per‑day' limits are a poor policy lever; instead, governments and schools should focus on specific harms (bullying, harassment, exposure to extreme content), and on identifying and supporting vulnerable subgroups through targeted screening and resources. That means funding measurement infrastructure (objective telemetry, robustness maps) and scaling interventions for high‑exposure tails rather than broad duration caps. — Reframing policy away from blanket screen‑time rules toward targeted, evidence‑based protections would change school rules, platform moderation priorities, public‑health funding and legal standards for youth safety.