Behavioural Abnormality Attention Deficit Hyperactivity Disorder ADHD http://purl.obolibrary.org/obo/HP_0007018 Attention Deficit-Hyperactivity Disorder SCDO:0000090 Attention Deficit Sufficient HP:0007018 Childhood Attention Deficit/Hyperactivity Disorder Attention Deficit Disorder Attention Deficits Attention deficit hyperactivity disorder (ADHD) manifests at age 2-3 years or by first grade at the latest. The main symptoms are distractibility, impulsivity, hyperactivity, and often trouble organizing tasks and projects, difficulty going to sleep, and social problems from being aggressive, loud, or impatient.