attention deficit-hyperactivity disorder

A disorder characterized by a marked pattern of inattention and/or hyperactivity-impulsivity that is inconsistent with developmental level and clearly interferes with functioning in at least two settings (e.g. at home and at school). When present, the symptoms of hyperactivity are most often present before the age of 7 years. There are three recognized presentations or subtypes from most to least common: combined type, inattentive/distractible type, hyperactive/impulsive type.