Short attention span Hyperactivity Attention deficit hyperactivity disorder Childhood attention deficit/hyperactivity disorder ADHD HP:0007018 SNOMEDCT_US:406506008 SNOMEDCT_US:7461003 Attention deficit-hyperactivity disorder UMLS:C1263846 HP:0001577 HP:0001576 Attention deficit HP:0006973 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.