ADHD (attention-deficit/hyperactivity disorder) is a neurodevelopmental disorder characterized by inattention, hyperactivity, and impulsivity. It often appears before school age and about half of children with ADHD continue experiencing symptoms into adulthood. Diagnosis involves observing a child's behavior in multiple environments, reports from parents and teachers, interviews, and tests. Potential causes include abnormalities in dopamine levels and the frontal-striatal brain region, as well as environmental factors like stress. Treatment options are drug therapy, behavior therapy, or a combination of the two.