Onset‑pattern test for youth harms

Policy and causal claims about youth wellbeing should be judged by whether they explain when harms began and which subgroups were affected. For example, a plausible theory should account for why adolescent suicide and mental‑health rises began around 2010, hit girls (especially preteen girls) hardest, and showed partial declines by 2018. — Using temporal and subgroup patterns as a basic falsification test raises the evidentiary bar for proposed causes (smartphones, curriculum, climate anxiety, etc.) and helps target research and policy more effectively.