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Attention-deficit/hyperactivity disorder (ADHD) is one of the most frequently encountered disorders in pediatric and adolescent medical practice. ADHD is a complex developmental disorder of brain and behavior that makes its initial appearance in preschool ages, persists into adolescence, and, in some individuals, into adult life.1 In 2007, the CDC summary of health statistics for U.S. children indicated that 4.5 million children (7%) between the ages of 3 and 17 years had been diagnosed with ADHD. The rate for boys (11%) was twice the rate for girls (4%).2 While the degree of persistence of this disorder into adulthood is still unclear, estimates from longitudinal studies suggest between 1% and 6% of the adult population has symptoms of ADHD.3
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Historically, symptoms of impulsivity, hyperactivity, and inattention were first attributed by Still (1902) to neurological disorder. Therefore, early clinical diagnosis were based upon presumptive "organic" etiological factors such as brain trauma, encephalitis, or other brain conditions that resulted in problems of attention, impulse control, emotional disregulation, and cognition. Gradually, however, the clinical diagnostic emphasis shifted to what Shelton4 labeled "symptom-based" description of the disorder, which preceded current classification systems such as the American Psychiatric Association's DSM-IV. In 2000, the empirically updated DSM-IV-TR5 was published and provides the current diagnostic criteria and ICD-9 codes for several subtypes of ADHD. These include (1) Attention-Deficit/Hyperactivity Disorder, Combined Type (314.01); (2) Attention-Deficit/ Hyperactivity Disorder, Predominantly Inattentive Type (314.00); (3) Attention-Deficit/Hyperactivity Disorder, Predominantly Hyperactive–Impulsive Type (314.01); and (4) Attention-Deficit/Hyperactivity Disorder, Not Otherwise Specified (314.9). While the first three subtypes are differentiated from each other on the basis of predominant clinical presentation, the fourth subtype is reserved for those patients who, despite the presence of prominent symptoms of inattention or hyperactivity– impulsivity, do not meet full diagnostic criteria for a specific ADHD subtype. Similarly, for adolescents and/or adults who currently have symptoms but no longer meet full criteria, the label "In Partial Remission" would be added to the diagnostic code (eg, 314.01—In Partial Remission). Table 9-1 presents the common signs and symptoms described for diagnostic purposes under the three primary domains of inattention, hyperactivity, and impulsivity.
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