Twelve cohorts of European, North American, and Chinese descent were aggregated in a meta-analysis of attention deficit and hyperactive disorder, revealing 12 associated loci. For the first cohort, cases were ascertained using the Danish Psychiatric Central Research Registrar and diagnoses were confirmed by psychiatrists according to ICD-10. The remaining studies included four parent-offspring trio cohorts and seven case-control cohorts. Cases were recruited from clinics, hospitals or through medical registries and diagnosed using research-based assessments administered by clinicians or trained staff. 19,099 cases and 34,194 controls of European ancestry were included in the current study.
