[MIM*143465] a behavioral disorder manifested by developmentally inappropriate degrees of inattentiveness (short attention span, distractability, inability to complete tasks, difficulty in following directions), impulsiveness (acting without due reflection), and hyperactivity (restlessness, fidgeting, squirming, excessive loquacity). To meet diagnostic criteria of ADHD as set forth in DSM-IV, the patient must display six or more specific symptoms of inattention, or six or more symptoms of hyperactivity and impulsivity, for at least 6 months to a degree that is maladaptive and inconsistent with developmental level. In addition, symptoms must have been present before age seven and there must be clear evidence of functional impairment in at least two settings (e.g., domestic, social, academic, occupational). SYN: hyperactive child syndrome.Attention deficit disorder, with or without hyperactivity, is a common, chronic behavioral disorder, most evident in children but often persisting through adolescence and into adulthood. The prevalence among children of school age is 3-15%, depending on how stringently diagnostic criteria are applied. As many as two thirds of patients continue to meet diagnostic criteria in adulthood, and it is estimated that 4% of the adult U.S. population is affected. Strong evidence suggests a genetic predisposition: about 25% of patients have at least one parent with the disorder, and it is about eight times more common in males than in females. Children with this disorder have a higher incidence of anxiety, depression, oppositional defiant disorder, academic underachievement, antisocial behavior, and substance abuse. Affected adults may manifest social and occupational maladjustment, chronic anxiety, substance abuse, and bipolar disorder. The diagnosis is strictly clinical. Central nervous system stimulants (dextroamphetamine, methylphenidate, pemoline) and the selective norepinephrine reuptake inhibitor atomoxetine administered regularly improve symptoms in about 80% of patients, but a positive response to these agents does not confirm the diagnosis of ADHD.