Attention deficits vary in ADHD

In a new study of children with Attention Deficit Hyperactivity Disorder (ADHD), researchers found that children differed significantly in the kinds of attention problems they exhibited.

Yehoshua Tsal, Tel-Aviv University; Lilach Shalev, Open University of Israel; and Carmel Mevorach, University of Birmingham, compared a group of children with ADHD with a control group of children. The results showed that deficits in sustained attention were the most common among the ADHD children, but deficits in selective attention, orienting attention and executive attention were also found. Tsal et al. report that these results refute some recent conclusions by other researchers who have stated the ADHD primarily represents deficits of executive function.

In this study, 27 children diagnosed according to DSM-IV criteria for inattentiveness or hyperactivity and impulsiveness were compared to 15 typical control children on four kinds of attention. The children were in primary school and had a mean age of 8.2 years. Children with below-normal IQ, impaired color vision or ADHD diagnosis by someone other than a psychiatrist or neurologist, were excluded from the study, along with those diagnosed with a neurological disorder other than ADHD or a mood, anxiety or conduct disorder.

Identifying attention deficits

Parents of all children completed the ADHD IV Rating Scale. Only five of the 27 ADHD students were on medication, and this was suspended during the study. All children in both groups were of average intelligence as measured by an abbreviated form of the Wechsler Intelligence Sale for Children. Eight of the ADHD students were diagnosed with a learning disability. All children were measured on tests of sustained attention (maintaining attention over a prolonged period), selective attention (focusing on relevant information while effectively ignoring distracting information), executive attention (inhibiting responses to irrelevant stimuli), and orienting attention (directing attention to a designated location and reorienting to a new location.

Besides comparing the control group to the ADHD group, researchers divided the control group into high- and low-scoring halves and compared them to high- and low-scoring ADHD children. Students who scored more than two standard deviations from the mean on at least one attention measure were identified as having a deficit in that area. Researchers assessed the frequency with which participants with a deficit in one area had deficits in other areas of attention. Boys were compared to girls, and children with ADHD plus learning disabilities were compared to children with ADHD alone.

On each measure, almost all the control students and some ADHD students scored within the average range. All students with ADHD and five control students were identified as deviating from the norm on at least one measure of attention. Problems with sustained attention were the most common and characterized most of the ADHD group. In addition, problems in each of the other three attention measures were found in more than half the ADHD group. Results showed that the four attention-test measures were independent, measuring different factors. In the executive attention task, the more accurate students tended to be slower and the less accurate were faster. Therefore, both speed and accuracy were incorporated into the executive attention score.

Students who had high scores on the ADHD criteria performed substantially lower than the low-scoring ADHD and control students on attention measures. However, this study is limited by its relatively small sample size. The present study shows that children diagnosed with ADHD suffer from deficits in at least one of the four types of attention measured. ADHD participants revealed different combinations of deficits, but almost all had problems sustaining attention while problems in executive attention were not as common as reported in other research. Overall, these ADHD children exhibited problems with effectively ignoring irrelevant distracting information, difficulty is sustaining attention over a relatively long period of time, and difficulty in benefitting from a cue that automatically attracts attention to a specified location. The precise distribution of these deficits across children with ADHD will require future large-scale studies.

Various deficits at play

This research does not support the idea that ADHD mainly reflects deficits in executive attention. These results show that ADHD represents a multitude of deficits in selective attention, sustained attention and the orienting of attention as well.

The complexity and diversity of ADHD is not fully explained by deficits in the one area of executive attention. Executive functions refer to a broad and loosely defined set of self-regulatory capabilities, such as working memory, planning and inhibitory control. Comparison of children with the inattentive and hyperactive-impulsive subtypes indicates that these groups share similar deficits in attentional functions. The only statistically significant differences in this small study were between the control children and those with ADHD.

The most prevalent deficit of children with ADHD is in sustained attention; problems with executive attention are no more dominant than problems with selective attention and orienting of attention. Tsal et al. conclude that ADHD can entail deficits in any one or any combination of the areas of selective attention, sustained attention, executive attention or orienting of attention.

Different children with ADHD possess divergent clusters of attention deficits. These researchers contend that the common practice of treating children with ADHD as an undifferentiated group may have adverse consequences. They believe it is reasonable to assume that the range and diversity of short- and long-term personal, behavioral, academic and social symptoms observed in various groups of children with ADHD result from deficits in different attentional systems.

“The Diversity of Attention Deficits in ADHD: The Prevalence of Four Cognitive Factors in ADHD Versus Controls”, Journal of Learning Disabilities, Volume 38, Number 2, April 2005, pp. 142-157.

Published in ERN May/June 2005 Volume 18 Number 5

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