77 rows · Attention deficit hyperactivity disorder (ADHD) is a common behavioral disorder diagnosed in roughly 10 percent of school-aged children and adolescents. There are three main subgroups of ADHD: Predominantly inattentive ADHD: inattention is the main characteristic, daydreaming is common. Adult attention deficit hyperactivity disorder (ADHD) facts. ADHD (attention deficit hyperactivity disorder) may occur in up to 6% of adults; it's marked by inattention, inability to focus, agitation, and, as the name suggests, hyperactivity. Attention deficit hyperactivity disorder is a form of behavioral illness that results in symptoms of distractibility, impulsivity, and/or bottomxxx.xyz: Roxanne Dryden-Edwards, MD.