Co-Occurrence of Attention-Deficit Disorder and Learning Disability: An Overview of Research.

Current studies concerning the co-occurrence, of attention deficit disorder and one or more learning disabilities are examined. Information is reported from four major aspects of the research: (a) statistical accounts of the prevalence of attention deficit disorder and the simultaneous occurrence of the two disorders; (b) subtypes of attention deficit disorder as they relate to learning disabilities; (c) findings and suggestions as to causes for the co-occurrence; and (d) educational implications based on current research.

Research acknowledges that learning disability and attention deficit disorder (ADD) frequently co-occur. In addition to significant inattentiveness, impulsivity, and hyperactivity, primary characteristics manifested in children diagnosed as ADD include "learning disorder" and "academic underachiever" (Marshall & Hynd, 1997; Stanford & Hynd, 1994). Estimates of co-morbidity of ADD and learning disability range from approximately 20% (Javorsky, 1996) to approximately 50% (Riccio & Jemison, 1998). Estimates of reports vary, depending on the way learning disability is defined or ADD is assessed. While this rate of co-occurrence has led some to theorize that the two disorders share overlapping deficits (Marshall & Hynd, 1997), other research concludes that ADD and learning disability are separate and distinct entities that often co-occur (Riccio & Jemison, 1998).

The purpose of this paper is to review the contemporary literature related to the cooccurrence of attention-deficit disorder (ADD), with and without hyperactivity, and specific learning disabilities. Factors common to children with either learning disability or attention deficit disorder as compared to common features of children diagnosed as having both ADD and learning disability are presented.

Attention deficit disorder occurs in an estimated 3 to 5% of school age children and is one of the most frequent reasons children are referred for evaluation (Stanford & Hynd, 1994). ADD was originally considered as "minimal brain dysfunction" and thus related to learning disability (Riccio & Jemison, 1998). However, the American Psychiatric Association (APA) gradually recognized it as a behavioral disorder separate from the developmental learning disabilities. The APA has recently further described the disorder as having subtypes: predominantly inattentive (or without hyperactivity), predominantly hyperactive, and combined type (Riccio & Jemison, 1998).

Stanford and Hynd (1994) found that Children with ADD have been found to be more disabled academically and cognitively than those without ADD. The disorder, which often occurs with learning disabilities, appears not only to have a negative effect on school achievement, but limits functional ability in other environments as well. While some studies have indicated an overlap in the area of attention between ADD and learning disability relative to cognitive behavior, their research did not support such an overlap in the behavioral domain.

Stolzenberg and Julkowski (cited in Marshall & Hynd, 1997) hypothesized that children with ADD experience difficulty decoding in reading and computing in math because working memory problems based on attention, interfere with absolute symbol systems necessary to these skill areas. Zentall and Ferkes (cited in Riccio & Jemison, 1998) expressed the view that inattention and disorganization, which relate to cognitive style, contribute to math computation deficiency. On the other hand, decreased IQ, memory, and reading ability seem to correlate with comprehension in reading and problem solving. Of interest are the findings that the cognitive tasks that are often predictive of reading disability have been found to be deficient in individuals with ADD. Among such tasks are naming, perceptual speed, and speed of cognitive processing (Marshall & Hynd, 1997). While lack of proficiency in these tasks has been shown to be predictive, Wood and Felton (cited in Riccio & Jemison, 1998) found attention variables themselves not to predict reading achievement. They found no significant predictive relationship between identification as ADD to either word identification or passage comprehension. The study also revealed no correlation between diagnosis of ADD and later reading ability.

Rather than aftentional factors underlying difficulty in attaining reading skills, some studies indicate that, like individuals with reading disorders, those with ADD may have phonological processing deficits or linguistic deficiencies that are predictive of reading disabilities (Riccio & Jemison, 1998). Not surprisingly, Cafts (cited in Riccio & Jemison, 1998) found in subjects with ADD and reading difficulties a relationship between reading disability and language processing difficulties. A number of studies conclude that language and verbal abilities, rather than the presence of an attention deficit, affect the acquisition and development of reading skills (Riccio & Jemison, 1998). Among children diagnosed with early language problems, Baker and Cantrell (cited in Javorsky, 1996) found an increased prevalence of learning disabilities and attention deficit disorder. Likewise, Cohen and Riccio (cited in Riccio & Jemison, 1998) provide evidence that the ADD characteristic of specific language impairment may be the strongest cause of reading problems in individuals with ADD. Javorsky (1996) also evaluated phonics and syntax in ADD groups, ADD/learning disability groups, and language learning disability groups. Upon comparison, the common factor proved to be the language learning disability and not the ADD. The ADD/learning disability groups and the language learning disability groups had similar measures, while the ADD group was significantly different. Indications are that the factor that was influential to the language test scores were not traits associated with ADD-attention, impulsivity, and hyperactivity; rather, the scores were most affected by the language learning disability.

Semrud-Clikeman (cited in Javorsky, 1996) postulated that it is the interaction of ADD and learning deficiencies inherent to learning disability and not a single factor of one of the disorders (e.g. aftention) that produces deficits that result in lower academic achievement and specific disabilities. Webster, Hall, Brown, and Bolen (1996) agreed that while ADD subjects displayed information processing problems, the presence of learning disability increased the negative impact of the attention deficit.

Subtypes

In 1980 the American Psychiatric Association reported inattention to be the primary symptom of attention deficit disorder, displacing hyperkinesis. As a result of this latest pronouncement, two subtypes were specified, nonhyperactive and hyperactive (Marshall & Hynd, 1997). Although children in both subtypes were assessed to be more impaired in some academic and cognitive areas, significant differences were discovered between the two groups (Stanford & Hynd, 1994). For example, Accardo, et al. (cited in Marshall & Hynd, 1997) explored the relationship between ADD and learning disability and noted a higher incidence of diagnosed learning disability in the nonhyperactive group (85.7%) versus the ADD group with hyperactivity (67.7%). Goodyear and Hynd (cited in Marshall & Hynd, 1997) support the contention that attention deficit disordertwithout hyperactivity is a "more attention/cognitive/anxious type of disorder in contrast to the more attention/behavior/impulsive aspects of attention deficit disordertwith hyperactivity" (p. 289). Barkley et al. (cited in Marshall & Hynd, 1997) appears to corroborate this finding as he reported that ADD students/with hyperactivity are more likely to be assigned to behavior disorder classes while ADD students without hyperactivity were more often placed in learning disability classes.

Rourke (cited in Marshall & Hynd, 1997) furthered this discussion when he found that attention deficit disorder/without hyperactivity displays a type of inattention symptomatic of nonverbal learning disorder, including math disabilities. Much additional research supports the hypothesis that children with learning disabilities share symptoms with children having attention deficit/without hyperactivity (Stanford & Hynd, 1994). Indications are that children with learning disabilities are more similar to those diagnosed with attention deficit disorder/no hyperactivity with respect to lethargy, social withdrawal, poor organizational skills and learning difficulties as compared to the more disruptive and aggressive aspects of attention deficit disordertwith hyperactivity (cited in Stanford & Hynd, 1994). Carlson et al. (cited in Marshall & Hynd, 1997) further specified that students with attention deficit/no hyperactivity were at greater risk for academic problems, especially math disabilities, than students with attention deficit disorder/with hyperactivity. Dykman et al. (cited in Marshall & Hynd, 1997) also found that students with attention deficit disorder/no hyperactivity were more disposed to math disabilities than those with attention deficit/with hyperactivity. Failure to gain automaticity with number .facts was considered to result in or contribute to the math deficit. Marshall and Hynd (1997) also compared ADD students with and without hyperactivity and found math achievement to be significantly lower for the latter group. The study suggests that the ability to "master abstract symbol systems" (p. 639) and acquire basic arithmetic skills in the early grades is disturbed by inattention. Likewise, Hynd et al. (cited in Javorsky, 1996) compared subjects with attention deficit disordertwith hyperactivity and those with attention deficit disordertwithout hyperactivity who had similar IQs. While the latter group performed more poorly in math, spelling, and reading, math was the only area where the differences in scores were significant. Sixty percent of the ADD/without hyperactivity students in the study had previously been diagnosed as having either a developmental reading disorder or a developmental math disorder. None of the ADD/with hyperactivity subjects had been diagnosed with either disorder.

Causes for Co-Occurrence

While etiology of the co-occurrence of ADD and learning disabilities may be secondary to effective intervention, beliefs about underlying causes may have a role in both formulation and implementation of teaching strategies. Understanding the ways in which ADD influences academic achievement may allow educators to better serve the learning disabled (Riccio & Jemison, 1998).

Some research has shown heredity to be a factor, not only in ADD, but also in reading disabilities. Studies suggest that while each of these heritable disorders may occur separately, their co-occurrence may also be genetic (Riccio & Jemison, 1998). Farraone (cited in Riccio & Jemison, 1998) noted a correlation between individuals with ADD and both parents with learning disabilities. Steinman, Steinman, Garzia, and Lehmkuhle (1996) suggest a single contributing factor for both attention deficit and learning disability. This study found visual attention to be deficient in students with reading disorders, and linked such clinical vision disorders to inattentive behavior. Conclusions were that the disruption in visual attention contributed to both information processing and attention deficit.

A causality which surfaces most frequently is perhaps the most obvious. Low academic achievement has been shown in many studies to result from the impulsivity, hyperactivity, attention problems, and cognitive deficits inherent in ADD (Riccio & Jemison, 1998). In that case, ameliorating the symptoms of ADD should, in fact, lessen the deficit in learning. Zentall (cited in Riccio & Jemison, 1998) agrees that rather than a common disabling factor for the disorders, academic problems are secondary to and a result of ADD. He contends, however, that the ADD characteristic that may lead to learning difficulties is a need for higher stimulation. This research suggests that additional and ongoing physical stimulation, such as is offered in interactive computer programs, could positively affect academic achievement by improving attention. Although much of the literature does recognize that ADD influences academic achievement, Baker and Cantrell (cited in Javorsky, 1996) found no evidence that lack of initial skill acquisition is caused by inattention, at least not to the extent as occurs with specific learning disabilities.

Contrary to the suggestion that ADD symptoms may lead to low academic achievement is the postulate that processing deficits or learning disabilities and academic failure could lead to a lack of concentration and attention (Riccio & Jernison, 1998). Frith (cited in Riccio & Jemison, 1998) also suggested that deficits, not only in attention but also in behavior, may occur as a result of reading difficulties. Acceptance of this implication leads to targeting primarily the academic deficiency for intervention rather than the behavior aspect of ADD.

Pennington et al. (cited in Riccio & Jemison, 1998) presents an interesting progression from these suggestions as to cause for co-occurrence. This study found a "reciprocal relationship" (p. 511) between inattentiveness and academic achievement, specifically reading achievement, that is affected by psychosocial factors. Inattention was found to have a negative effect, not only on reading achievement but also on attitude toward reading and reading at home with parents. The relationship was noted in reverse, as well. Positive attitude toward reading, along with high reading achievement and reading at home, increased attentiveness in school. In essence, while inattention affected reading achievement, reading achievement appeared to influence attentiveness.

Educational Implications

The relationship between ADD and learning disability is not fully understood and the causality of co-occurrence not agreed upon. As a result, assessment and intervention must include a variety of measures. Because ADD is often viewed as a behavioral disorder, referrals are generally based on behavioral problems (Riccio & Jemison, 1998). The significant cooccurrence of reading/learning disabilities and ADD, however, requires that not only behavioral but also academic areas be assessed. Riccio and Jemison (1998) advise that young children manifesting the behavioral symptoms of ADD should be monitored for learning disabilities. Conversely, children referred for early reading and language acquisition difficulties should be given a comprehensive assessment which includes behavioral domains (Riccio & Jemison, 1998). For example, for students who are doing poorly in an academic area such as math, consideration should be given as to whether inattention is a contributing factor (Marshall & Hynd, 1997). Studies indicate that concurrent academic, language, and behavioral interventions are needed for ADD and learning disabilities (Riccio & Jemison, 1998). Rowe and Rowe (cited in Riccio & Jemison, 1998) determined that given the "reciprocal nature of the relationship between reading achievement and inattention" (p. 357), instructional strategies must target both areas simultaneously. It has even been discovered that appropriate ADD interventions may improve reading and other academic areas incidentally (Riccio & Jemison, 1998). Early interventions for the co-occurring disorders may improve a child's prospect for success in and out of the academic setting.

Summary

Although there is general agreement that learning disability and attention deficit disorder often co-occur, there is no consensus as to the nature of the correlation. Neither is there agreement about causality. Much of the literature suggests that learning disabilities are more frequently associated with the subtype of attention deficit disorder that is predominantly inattentive rather than hyperactive. Evidence that such an association exists should help in the identification of specific ADD subtypes. For children diagnosed with attention deficit/no hyperactivity there may be opportunity for early preventive measures to be implemented in academic areas. Medication in combination with specialized instruction may be indicated (Riccio & Jemison, 1998). Intervention other than medication that influences the behavioral aspects of ADD, along with academic interventions appropriate to the learning disability, may enhance and improve learning. There is need to further explore the link between these two disorders. The nature of the co-occurrence should be more precisely expressed and educational interventions undertaken in order to more effectively remediate these complex disorders.

References

Javorsky, J. (1996). An examination of youth with attention deficit/hyperactivity disorder and language learning disabilities: A clinical study. Journal of Learning Disabilities, 29(3), 247-259.

Marshall, R. M., & Hynd, G. W. (1997). Academic underachievement in ADD subtypes. Journal of Learning Disabilities, 30(6), 635-643.

Riccio, C. A., & Jemison, S. J. (1998). ADHD and emergent literacy: Influences of language factors. Reading and Writing Quarterly, 14(1), 43-59.

Stanford, L. D., & Hynd, G. W. (1994). Congruence of behavioral symptomology in children with ADD/H, ADD/WO, and learning disabilities. Journal of Learn Disabilities, 27(4), 243-254.

Steinman, B. A., Steinman, S. B., Garzia, R. P., & Lehmkuhle, S. (1996). Vision and reading III: Visual attention. Journal of Optometric Vision Development, 27(1), 428.

Webster, R. E., Hall, C. W., Brown, M. B., & Bolen, L. M. (1996). Memory modality differences in children with attention deficit disorder with and without learning disabilities. Psychology in the Schools, 33(3), 193-201.

Janice Maynard, M. Ed., J. Larry Tyler, Ed.D.,Mit Arnold, Ed. D. Department of Curriculum and Instruction, The University of Mississippi.

Correspondence concerning this article should be addressed to Dr. Mit Arnold, Department of Curriculum and Instruction, 139 School of Education, The University of Mississippi, University, MS 38677.