Hyperactivity Disorders of Childhood

It has been estimated that by DSM-IV criteria one of every three children referred to psychiatric clinics is diagnosed as suffering from an attention-deficit hyperactivity disorder (ADHD). Conservative estimates place the prevalence of this condition as 2 to 6 percent of all children in the United States, with some studies reporting a prevalence of 17 percent. By 1987 a total of 6 percent of all public elementary school children in the United States were receiving stimulants (1), and within the last five years use of methylphenidate is up 500 percent (2). Clearly, attention-deficit hyperactivity disorder is a problem of great magnitude and importance, interfering with the child's social, emotional, academic, and vocational adjustment.

In the United Kingdom, however, the diagnosis follows ICD-10 criteria for hyperkinetic disorders and requires direct observation of the criteria symptoms as well as evidence of more pervasive presence of the symptoms both in school and at home. The prevalence of hyperkinetic disorder in the U.K. is lower than in the United States, approximately 2 percent; the use of stimulants is much less; and the therapeutic emphasis is not on stimulant drugs but on social, educational, and behavioral modalities.

This book, edited by Seija Sandberg of the Royal London Hospital, is a comprehensive review of how the ADHD-hyperkinetic disorder syndrome is seen in countries other than the United States. Of the 13 chapters, only one, by Sheryl Olson on developmental perspectives, is from the U.S.; the rest are from Canada, the United Kingdom, Sweden, the Netherlands, Australia, France, Germany, and Japan. The references, however, are worldwide and appear complete to the mid-nineties.

The book begins with the historical development of the hyperkinetic syndrome, reviews epidemiological approaches, and then discusses clinical diagnosis and the relationship of core symptoms of hyperactivity to conduct disorders, aggression, and learning problems. The role of attention and the role of biological problems have their own chapters. The significance of sex differences, cross-cultural differences, school, and psychosocial issues are considered, and various approaches to treatment and outcomes measurement are described.

The book emphasizes that ADHD-hyperkinetic disorders, as defined by DSM and ICD-10, are a syndrome—a cluster of symptoms that may arise from diverse etiological factors, have varying natural histories, require different treatment approaches, and result in different outcomes. As Sandberg, Day, and Trott point out, "Many U.K. clinicians see little reason to use the concept of hyperactivity," citing "the lack of demonstrated aetiological or prognostic homogeneity in children with hyperactivity disorder" (page 70).

Unfortunately, no consistent biological marker or identifiable genetic abnormality to define the hyperactivity group has yet been found. Diagnosis must therefore depend on evaluation of the behaviors said to characterize the syndrome—attention, impulsiveness, and overactivity. However, the dimensions of these behaviors may be blurred not only in the eye of the beholder but by the lack of a clear dividing line between normal and abnormal, the characteristics of questionnaires, the ubiquity of the symptoms in other disorders, and the inert and apathetic presentation of some of the children.

A key disturbance in the hyperkinetic syndrome is attention, with hyperkinetic children having "an inability to modulate their physiological state according to task or situation demands," to quote Jaap Van der Meere (page 133). This problem with modulation is seen in the hyperkinetic child's reaction to stimuli. The hyperkinetic child responds slowly and inaccurately rather than quickly and immediately.

For example, the only consistent finding in tests of dichotic listening, paired associative learning, visual search, and continuous performance suggests that task performance improves when the rate of presentation of stimuli increases, and decreases when the rate of presentation decreases. Because the task efficiency of children with attention deficit is sensitive to state manipulation, Van der Meere suggests replacing the term "attention deficit" with "state regulation deficit" (page 138). It remains to be seen if state regulation deficit is unique to the hyperkinetic syndrome.

Concerning learning disability, Jim Stevenson presents some evidence in chapter 11 to suggest that hyperactivity and reading disability show some common causes, possibly a shared genetic etiology. The problem with these data is that Stevenson defines reading disability as reading age significantly below that expected on the basis of chronological age and IQ. Because many factors other than age and intelligence can be implicated in impaired reading, my colleague and I have reserved the term "specific reading disability" for children with specific central nervous system processing defects (3). While the proportion of hyperactive children with specific reading disability is in the 20 percent range, it is no higher than the prevalence of specific defects of central nervous system processing in the normal population. The learning problems of these children will not respond to the stimulant medication that may be effective for hyperactivity.

Although few new insights are revealed in this book, it does cover the field with depth, clarity, and expertise. As would be expected with chapters written by different authors dealing with overlapping topics, there is redundancy in concepts, and particularly in references. However, it is refreshing to review the thoughts of workers other than those whose work we read in our American journals. It is obvious that the authors of this book have read our papers and have evaluated our findings.

Dr. Silver is professor and director of child and adolescent psychiatry in the department of psychiatry and behavioral medicine at the University of South Florida in Tampa.