Common Danish standards in prescribing medication for children and adolescents with ADHD.

Assessing whether symptoms of attention-deficit hyperactivity disorder (ADHD) in children are age-inappropriate 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-grade. The Danish system, with its restrictive approach to medication and clear diagnostic guidelines seems to have avoided a systematic bias of ADHD medication in young children reported in other countries.