This nationwide longitudinal study used Norwegian health registry data to track the incidence of new ADHD diagnoses and medication initiation in children and adolescents aged 3–17 years from 2016 to 2024 (n=52,149 incident cases), and examined sociodemographic factors linked to medication initiation in 38,749 individuals diagnosed 2016–2023.
Overall ADHD incidence more than doubled from 4.4 to 9.0 per 1,000; the sharpest rise was in females aged 14–17 (3.1 → 11.4 per 1,000, ~3.7-fold). Medication initiation within 12 months rose modestly from 72.8% to 78.4%, but shifted from early (0–3 months) to delayed (4–12 months) timing. Immigrant background and parental birth in Africa or Asia were linked to lower odds of initiation; lower paternal education was linked to higher odds.
- Private-sector (non-publicly funded) diagnoses are not captured by the Norwegian Patient Registry, potentially undercounting incident cases. - Non-pharmacological treatments (behavioral therapy, psychoeducation) are not recorded in the registries, so it is unclear whether delayed initiation reflects active use of behavioral interventions. - Registry data lack clinical granularity (e.g., symptom severity, comorbidities) needed to fully explain treatment decisions.
Clinicians should be alert to the inattentive ADHD presentation in adolescent females, a group whose diagnosis rate nearly quadrupled over this period. Disparities in medication initiation by parental background signal a need for culturally sensitive outreach to ensure equitable access to care.
