Assessing whether symptoms of attention-deficity hyperactivity disorder (ADHD) in children are ageinappropriate is essential. Hence, comparing children within one school grade is problematic and the risk of applying relative standards is inherent. Being young-for-grade increases the likelihood of receiving medication in countries with high prevalence of ADHD medication. We test the same hypothesis in a cohort of 418,396 children and find no difference between children who are young-for-grade and old-for-gade. The Danish system, with its restrictive approache to medication and clear diagnostic guidelines seems to have avoided a systematic bias of ADHD medication in young children reported in other countries.
European Child and Adolescent Psychiatry, 2014, Vol 23, Issue 9, p. 841-844