Conclusion

The reader can judge for himself or herself whether the label ADHD is better than MBD in terms of the accuracy of diagnosis in terms of characterizing the problems of these children. The former is descriptive, whereas the latter implies a neurological etiology. The symptoms now used to identify ADHD children are the same as in the days of MBD, with changes in wording and in the groupings of symptoms. The gain, not to be overlooked, is that the definition of ADHD is less inclusive than the definition of MBD. To make a statement that will appear even more ludicrous to those working on classification, I believe that one might do almost as well in categorizing ADHD by using only one or two items in each category of DSM-IV (inattention, HYP, and IMP). Each item selected would be rated for severity on some 4-5-point Likert scale, e.g., "often fails to give close attention to details" or "makes careless mistakes in schoolwork or other activities," is often "on the go" or "often acts as if driven by a motor, often has difficulty awaiting turn." The first mentioned item may not be a pure item in that it appears to also involve impulsive behavior. Nonetheless, a limited set of items might do the job about as well as all items now used, as none of these requires a severity rating.

Whether the basic deficits in ADHD children are in the areas of attention, self-regulation, EF, or some other process continue to be hotly debated issues. The boundaries among inat-tention/ attention, working memory, arousal, EF, and effort are more than just somewhat obscure. One could, for example, substitute terms like the following for ADHD: intention disorder (14,15), inhibition disorder (12,22,50,234), motivation disorder (53,62,75,88,235), short-term memory disorder (140,141), rule-based disorder (74,84,93), or even MBD if we remove LD from the definition. Almost any label would be acceptable, if truly descriptive or better explanatory of the symptoms of these children.

The problem with MBD is that it is an onerous term that is less attractive to parents and teachers than ADHD. In any case, the label ADHD should be replaced if a better descriptor can be found. ADHD children differ from normal controls in having deficits in functioning or structure of many parts of the brain and not just the frontal lobes (see ref. 236 for latest ERP studies; 237 for neural substrates involved; 238 and 239 for gene research; 240 for corpus cal-losum; 241 for temporal and parietal lobes; and 242 for caudate nucleus; See also Chapter 6). In addition to involvement of cortical areas, there is also evidence for differences in ADHD children and controls at the level of the control centers regulating spinal reflexes (243-246).

Is inattention a trivial problem, as Barkley (229) suggests? I think not. It is one of the most important executive functions. Research on this measure should go beyond the usual topics of sustained and selected attention. Most important is the quick shifting of attention between within and without. This occurs within a few milliseconds and has an immediate effect on directional changes in heart rate (43,44,247). The approach by Posner et al. (248,249) is basic to this issue, although I found in unpublished work that Posner's paradigms are often too difficult for children.

We now know with reasonable certainty that the most important factor predisposing to ADHD is inheritance from a long line of ancestors (see Subheading 8.1, genetic causes and later chapters in this book). The environmental influences most important in accounting for some ADHD cases, probably not the common variety seen every day in clinics, would include such factors as inadequate nutrition, intrauterine growth problems, developmental deficits leading to brain injury, accidents injuring the brain, lead poisoning, and fetal alcohol syndrome (see Section 8.). Also, it is clear from our work and others (15,22,93) that rewards, as well as stimulant medication, have the effect of normalizing the performance of ADHD or MBD children in situations demanding close attention and effort.

Another issue of importance is that of categorical vs dimensional analysis. Research is scant in this area and more is needed. Our research reported above (149) favors dimensional analysis. New research should utilize ratings that are comprehensive enough to cover the major dimensions of ADHD including aggression, modeled after the research that has been done on the mmpi to identify important combinations of disorders. Some combination of the Achenbach CBCL, the long-form Conners Rating Scales, and other relevant items from structured interviews should be used. Separate scales should be constructed for parents and teachers. Teacher ratings are better than parent ratings for purposes of identifying children deviant from their normal age-matched controls. Teacher and parent ratings are poorly correlated even when the same items are being rated, and factor analyses of ratings that include both teachers and parents segregate more by who does the rating than by the nature of the item (149).

Turning to the merits of categorical analysis, DSM-IV provides the possibility of classifying subjects in any one category into a large number of other co-occurring categories. The problem is that most research, which targets any one diagnostic category, tends to ignore the co-occurring disorders, and in ADHD the most frequent ones are learning disabilities and ODDs. The latter identifies the type of HY child that Dykman et al. (147) referred to as the ADDHA. Of course, it would not be necessary in future modifications of DSM-IV to include LD or aggression as a part of the definition of ADHD, if investigators were more rigorous in defining co-occurring disorders and not treating LD or ADHD as pure categories unless children with only one disorder were recruited. Pure types, however, are difficult to find.

Finally, would it be possible, with some combination of tests or rating forms now on the market plus laboratory tests, to develop a classification system that is realistic both in subtyping and in identifying the underlying problems of ADHD and LD children? For LD, phonetic abilities should be assessed because this is the problem for many of them (250). This assessment should include standardized tests of reading, spelling, and arithmetic, including verbal and performance IQ. Laboratory tests that would seem to be of value in pinpointing the underlying defects are the go/no-go tests, readiness to respond tests with different delays, the continuous performance task, and the distraction tasks used in our early MBD studies (see Section 2.), the stop task (234), and conditioning tests involving frustrative reward and relatively long delay intervals before reinforcement. The behavioral part of the test battery should assess HYP, impulsiveness, inattention, learning problems, and aggression (e.g., frustrative nonreward). Paradigms should be designed to allow for autonomic and brain function measures to be taken in the laboratory while subjects are performing the behavioral tests. Once worked out, software could be developed and marketed for use by clinicians with perhaps just behavioral measures and reaction times. This suggested approach calls for some consideration of reversing the usual course of external validation, going from tests to diagnosis rather than from diagnosis to tests, and a greater inclusion of what we have learned about the relationships between behavior and brain function in the diagnosis and treatment of the disorder.

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