BACKGROUND: Preventive psychiatry requires longitudinal, transdiagnostic data from before adolescence, yet such data are scarce. We propose a nationwide, digital, open cohort in Japan to track mental health trajectories from birth to late adolescence using multi-informant assessments (caregivers and adolescents) within a transdiagnostic, biopsychosocial framework. Diagnosis-open recruitment will combine community-facing dissemination with clinically linked neurodevelopmental enrichment (e.g….
