COMORBIDITY OF LEARNING AND ATTENTION DISORDERS: Separate But Equal
Section snippets
PROBLEM OF COMORBIDITY
Complicating the process of diagnosis and treatment is the problem of comorbidity: the fact that many children who present with learning and attention disorders actually have symptoms of both. As discussed later, current research evidence indicates that these are separate, but overlapping, disorders.37 Although it is tempting to pursue differential diagnosis to isolate one from the other, the reality is that comorbidity is so common that diagnosis of either type of disorder always should
HISTORICAL PERSPECTIVE
The problem of comorbidity is better appreciated when earlier descriptions of learning and attention disorders are considered. From the earliest conceptualizations in this century, the disorders were intertwined and not conceptually distinguished until the past 20 years. At the turn of the century, Still45 argued that patterns of behavior characterized by impulsive, overactive behavior represented “a morbid failure of self-control” and were due to constitutional, not environmental, causes. Kahn
SEPARATE OR OVERLAPPING DISORDERS?
Learning disabilities and ADHD are not always viewed as involving separate disorders. McGee and Share24 suggested that ADHD was actually the consequence of learning disability, representing the cumulative effects of academic difficulties on motivation and interest in school. One well-known study reported that those children who showed both reading disability and ADHD did not have a true comorbid association. In this study, the behavioral pattern associated with ADHD in isolation of reading
DEFINITION ISSUES IN ATTENTIONAL DISORDERS
In current conceptualizations, attentional disorders are subsumed under the rubric of ADHD. It is important to recognize that diagnostic criteria for ADHD are not based on formal assessment of cognitive skills. Rather, ADHD is a behavioral disorder with implications for cognitive function.14 The primary defining characteristics are behavioral and historical. There are currently no widely accepted performance-based indicators of ADHD that can be used as a primary vehicle for diagnosis. ADHD is
DEFINITION ISSUES IN LEARNING DISABILITIES
In the area of learning disabilities, definitional issues have been investigated carefully over the past 10 years. A learning disability is a disorder of cognition that manifests itself as a problem involving academic skills. The federal definition of a learning disability,50 adopted in 1968 and still the basis of federal legislation on learning disabilities, clearly highlights the importance of cognitive processes:
Children with specific learning disabilities exhibit a disorder in
ROLE OF IQ TEST SCORES
It is noteworthy that most states require an IQ score for the identification of a child with a learning disability, and more than two thirds require some form of discrepancy between IQ and achievement scores.18 This means that learning disabilities can be diagnosed only with psychometric tests involving measures of both IQ and academic achievement. For example, many states require a difference of approximately one standard deviation (15 points) between IQ and achievement to qualify for services
COGNITIVE PROCESSES IN LEARNING DISABILITIES
For children with reading disabilities, recent evidence converges in showing that most disorders involve deficits at the level of the single word (i.e., word recognition skills) and not in text processing ability (i.e., comprehension). The cause of single word reading deficits clearly lies in the child's language skills, specifically in areas involving phonologic processing skills.11, 34 This type of reading disability corresponds to contemporary conceptualizations of dyslexia as a
COGNITIVE FUNCTIONS IN ADHD
On average, cognitive functions can be impaired in children with only ADHD. They are, however, different from those apparent in children with reading disabilities, largely reflecting abilities subsumed under models of attention and executive functions.4 Although measuring some components of attention is well established, executive functions are difficult to measure precisely and are therefore currently of limited assistance in the assessment of individual children with ADHD.4, 14 The tests used
PREVALENCE
The problem of comorbidity becomes clear when studies of the prevalence of these disorders are considered. For reading disabilities, the most common form of learning disability, estimates generally range up to 15%, whereas prevalence estimates for attention disorders range from 3% to 7%.3, 40, 48 Prevalence figures, however, vary widely due to differences in ascertainment of the samples, selection criteria, and diagnostic procedures. These estimates increase when comorbidity enters the picture.
PROGNOSIS OF LEARNING AND ATTENTION DISORDERS
Comorbidity becomes an important consideration when it is recognized that all of these childhood disorders are chronic and persistent and typically influence the child in adulthood. In one study, 30% to 50% of children with ADHD had symptoms that persisted into adulthood.5 Wood and Felton53 found that childhood onset of ADHD reduced the number of years of high school and college education but did not specifically impact the development of reading skills. This study also reported that childhood
ASSESSMENT
When the issue of comorbidity is considered, children who are suspected of learning disabilities and ADHD need careful, systematic, and comprehensive evaluations. This does not mean that the child necessarily needs an interdisciplinary evaluation in which different specialists are consulted. Rather, it means that the assessment must be sufficiently comprehensive to provide at least screening for both learning and attention disorders.15, 37 Any child suspected of a learning disability needs a
TREATMENT
The ultimate reasons for highlighting the importance of comorbidity are the implications for treatment. Although there is currently insufficient research to demonstrate interactions of treatment outcomes and potential sources of comorbidity, treatment interventions should take into account comorbidity until such research provides more direction. A child can receive a careful assessment of academic skills, be identified with a learning disability, and be placed in an academic remediation
CONCLUSIONS
Comorbidity is an important consideration in the assessment and treatment of children with developmental disabilities. Children with either learning disability or ADHD often present with both disorders. It is important to assess for both disorders in any child and to develop a treatment plan that addresses both disorders when necessary. Approaches to intervention that address only part of a child's presenting problems are less likely to be successful. Comorbidity is an issue that always should
ACKNOWLEDGMENT
The assistance of Rita Taylor with manuscript preparation is gratefully acknowledged.
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Cited by (65)
Impairments in speech and nonspeech sound categorization in children with dyslexia are driven by temporal processing difficulties
2011, Research in Developmental DisabilitiesCitation Excerpt :Other researchers (Roach, Edwards, & Hogben, 2004; Heath, Bishop, Hogben, & Roach, 2006; Hazan, Messaoud-Galusi, Rosen, Nouwens, & Shakespeare, 2009) have disagreed to attribute the observed problems on auditory tasks to a specific perceptual processing deficit of certain stimulus characteristics (e.g., temporal cues), but have explained the deficit by task demands. Most auditory processing tasks, like the ABX-identification task used in this study, also rely on non-sensory factors such as attention and verbal short-term memory, which have been shown to be impaired in persons with dyslexia (Ramus & Szenkovits, 2008; Fletcher, Shaywitz, & Shaywitz, 1999). We agree that also in our study these non-sensory factors may have decreased the overall performance of the children with dyslexia, but these non-sensory factors cannot explain why the labeling problems in dyslexics were significantly worse in the temporal versus the nontemporal conditions since task demands were equal across conditions.
Examination of the relationship between ADHD and learning disorder in Primary School Children in Tehran
2011, Procedia - Social and Behavioral SciencesWritten composition performance of students with attention-deficit/ hyperactivity disorder
2013, Applied Psycholinguistics
Address reprint requests to Jack M. Fletcher, PhD, Department of Pediatrics, Center for Academic and Reading Skills, 7000 Fannin—UCT 2478, University of Texas–Houston Medical School, Houston, TX 77030
Supported in part by grants from the National Institute of Child Health and Human Development: PO1–HD21888, Psycholinguistic and Biological Mechanisms in Dyslexia, P50–HD25802, Center for Learning and Attention Disorders, and R01–HD30885, Early Interventions for Children with Reading Problems.