Is Adult ADHD a Childhood-Onset Neurodevelopmental Disorder? Evidence From a Four-Decade Longitudinal Cohort Study

Objective: Despite a prevailing assumption that adult ADHD is achildhood-onsetneurodevelopmentaldisorder,noprospective longitudinal study has described the childhoods of the adult ADHD population. The authors report follow-back analyses of ADHD cases diagnosed in adulthood, alongside follow-forward analyses of ADHD cases diagnosed in childhood, in one cohort. Method: Participants belonged to a representative birth cohort of 1,037 individuals born in Dunedin, New Zealand, in 1972 and 1973 and followed to age 38, with 95 % retention. Symptoms of ADHD, associated clinical features, comorbid disorders, neuro-psychological deficits, genome-wide association study-derived polygenic risk, and life impairment indicatorswere assessed.Data sources were participants, parents, teachers, informants, neuro-psychological test results, andadministrative records.AdultADHD diagnoses used DSM-5 criteria, apart from onset age and cross