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A high level of activity and short attention span are part of normal development in infants and toddlers. Many typically developing preschool children continue to manifest these same characteristics. When they develop impulse control around 4 years of age, overactive and distractible behaviors diminish. Attention span, activity level, persistence, and adaptability to change also reflect a child’s temperament or behavioral style. These traits may affect learning and social interactions when they are discordant with expectations of the child’s environment—of teachers, parents, and peers.


More than a century ago, British physician George Still described a behavior pattern that presented with restlessness and inattentive and overaroused behaviors and that involved a child’s inability to internalize rules and limits. He attributed the condition to a defect in moral character. Following the worldwide epidemic of influenza with encephalitis of 1917 to 1918, some of the recovering children displayed symptoms of restlessness, inattention, impulsivity, easy arousability, and hyperactivity; it was described as a postencephalitic behavior disorder. A description of attention deficit hyperactivity disorder (ADHD) has appeared in subsequent versions of the Diagnostic and Statistical Manual of Mental Disorders (DSM) of the American Psychiatric Association. As newer neuropsychological and clinical research emerged, the name of the disorder changed from hyperkinetic impulse disorder (DSM-II), to attention deficit disorder (DSM-III), and most recently to attention deficit hyperactivity disorder (DSM-IIIR, DSM-IV, and the latest version, DSM-IV-TR, published in 2000).


Core symptoms of ADHD are inattention, hyperactivity, and impulsivity. ADHD is the most common and most extensively studied biopsychosocial problem in school-aged children. It is a chronic condition that persists into adolescence and adulthood in 60% to 80% of individuals diagnosed with ADHD during childhood.1,2


Attention deficit hyperactivity disorder (ADHD) has been identified in children in every country and culture studied. The prevalence rate of ADHD varies depending on diagnostic criteria, the population studied, and the number of sources used to establish a diagnosis. The absence of a biologic marker to establish a diagnosis of ADHD and dependency on parent and teacher reports of behavior is a challenge to research on prevalence. A prevalence of 4% to 12% was found in an analysis of 11 studies using community samples. In a recent national study, 8.7% of children met DSM-IV criteria for ADHD.3 Poor children were more likely to fulfill criteria for ADHD. However, wealthier children were more likely to receive regular medication treatment. Less than half of children meeting DSM criteria for ADHD in this study had received either a diagnosis or regular treatment for ADHD. There is a male predominance of ADHD with a male-female ratio of 3:1 for the combined type and 2:1 for the predominantly inattentive type. In community samples, predominantly inattentive ADHD is the most prevalent subtype, about 1.5 times more common than the combined type and twice as common as the hyperactive/impulsive subtype. School-aged and adolescent girls are more likely to comprise the inattentive subtype. ADHD does occur in ...

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