The aetiology of attention-deficit/hyperactivity disorder (ADHD) and hyperkinetic disorder (HKD), a severe form of ADHD, is not well understood but genetic and environmental factors are thought to contribute.
HKD diagnosis was identified for children on or after their fifth birthday, as per Danish National Hospital records and the Danish Psychiatric Central Registries.
Of the 101,041 pregnancies enrolled in the DNBC, 64,322 were included for the cohort for analyses of HKD diagnosis and ADHD medication and a total of 40,916 pregnancies included in the cohort for analysis with reported SDQ behavioural outcomes available as reported by primary caregiver.