Importance Attention-deficit/hyperactivity disorder (ADHD) affects 39 million people worldwide; in isolation, it doubles annual health care costs and, when associated with comorbid mental health problems, it quadruples the costs.Objective To compare the education and health outcomes of schoolchildren treated for ADHD with their peers.Design, Setting, and Participants In this population-based cohort study, individual-level record linkage was performed of 8 Scotland-wide administrative databases covering dispensed prescriptions, admissions to acute and psychiatric hospitals, maternity records, annual pupil census, examinations, school absences and exclusions, and unemployment. The study cohort comprised 766 244 children attending Scottish ...