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Friedman, L. M., Rapport, M. D., Raiker, J. S., Orban, S. A., & Eckrich, S. J. (2016). Reading comprehension in boys with ADHD: The mediating roles of working memory and orthographic conversion. Journal of Abnormal Child Psychology. Advance online publication. doi:10.1007/s10802-016-0171-7

Summary by Dr. Jessica Church-Lang

Overview

Attention-deficit/hyperactivity disorder (ADHD) is a diagnosis given when levels of hyperactivity, impulsivity, or inattention impair normal function. The Centers for Disease Control and Prevention estimates that as of 2011, approximately 11% of children ages 4–17 in the United States had been diagnosed with ADHD, though the numbers varied widely by region. ADHD has been shown to affect executive control, which is thought to allow cognitive flexibility, such as adjusting to changing circumstances, receiving error feedback, and holding task details in mind (Willcutt, Doyle, Nigg, Faraone, & Pennington, 2005). Importantly, ADHD co-occurs with many other disorders; for example, children with ADHD struggle with reading about 25% to 40% of the time (Willcutt & Pennington, 2000). Struggling readers also have greater attention problems than nonstruggling readers (Cho et al., 2015).

  The hierarchical components proposed and analyzed by Friedman et al. (2016) for their effect on reading ability in children with ADHD. Purple stars indicate the primary findings. Adapted from Friedman et al. (2016).

Friedman, Rapport, Raiker, Orban, and Eckrich (2016) studied 61 boys ages 8–12 (31 with a diagnosis of ADHD and 30 typically developing). They tested whether task control abilities (in this paper, termed the central executive), phonological short-term memory, visuospatial short-term memory, or orthographic conversion abilities (translating letters into sounds) independently contribute to reading difficulties in children with ADHD. Memory is important to reading because the semantic meaning of words must be kept in mind while the brain translates letters on the page to the sounds of language. This paper is novel in its attempt to separate impairment of the central executive from phonological and visuospatial short-term memory impairments in children without low reading test scores indicative of reading difficulties.

Friedman and colleagues used parent, teacher, and clinician ratings of ADHD symptoms to assess ADHD severity in all 61 children, and the 12 children on ADHD medication refrained from taking it for 24 hours before the testing session. All participants completed the reading comprehension subtest of the Kaufman Test of Educational Achievement (to assess reading comprehension ability), the letter-number sequencing subtest from the Wechsler Intelligence Scale for Children – Fourth Edition (to assess phonological working memory), and a computerized serial dot position task (to assess visuospatial working memory). Central executive processing was estimated as the shared variance across the two working memory tests. Orthographic conversion speed was measured with timed reading of a 203-word passage from a second-grade text, and orthographic conversion accuracy was measured with the reading decoding subtest of the Kaufman Test of Educational Achievement. These two measures were combined to reflect the overall orthographic conversion ability.

Parent and teacher attention behavior scores were significantly higher for the 31 children with ADHD than for the 30 children in the typically developing group. Diagnosis of ADHD related significantly to reading comprehension scores, such that children with ADHD scored significantly lower on reading comprehension than their peers. Orthographic conversion ability and the central executive ability mediated ADHD-related reading comprehension differences (explaining 61% of the variance), and phonological and visuospatial working memory abilities were not significant.

Strong letter-to-sound understanding and good overall task control best predicted reading comprehension abilities, and these skills were particularly impaired in the sample of children with ADHD.

Key Findings

This paper tests models of relationships between ADHD, reading comprehension, and task control.

Impact of Control Mechanisms on Reading

Detecting tiny changes in print representing different letters of our language and reading vastly different handwriting require strong visual abilities. Holding the meaning of a sentence in mind while cycling through proper pronunciation of words, given different letter-to-sound circumstances, requires strong phonological and memory abilities. This paper is a good example of how abilities beyond reading and letter knowledge (e.g., working memory tests) can contribute to reading comprehension. The authors replicate a known finding that task control is critical to reading and in this case point to specific impairment of global control processes (e.g., the central executive) in ADHD rather than being limited to task-specific control processes (e.g., phonological working memory). Future studies should explore the effects of ADHD medication (e.g., whether it also ameliorates reading problems) and identify the underlying brain mechanisms that separate children with ADHD who do not have reading problems from those who do.

Impact of Co-Occurring Reading Difficulties With ADHD

The authors find lower reading comprehension scores in children with ADHD, which is consistent with the known high co-occurrence of reading impairments and ADHD. However, in this sample, the children with ADHD were not technically struggling readers (they had average standard scores on reading tests). The authors do not report whether any of the sample had diagnosed learning difficulties. The larger message of this paper, then, could be that children with ADHD are at higher risk for underperformance on reading tests than their peers, even in cases where they have no diagnosed reading difficulties. It is interesting to reflect on why hyperactivity, impulsivity, or inattention symptoms appear to travel so often with reading difficulty and on what environmental variables might be at play (children who have attention difficulties likely spend less time reading overall). Further, as the children with ADHD were unmedicated during testing, it remains to be seen whether these reading comprehension or central executive difficulties would be resolved with alleviation of the attention symptoms through medication or behavioral therapy.

Implications and Recommendations

These results have implications for our understanding of reading in at least two ways.

Recommendation 1

Parents of children at risk for or with ADHD should promote reading behaviors at home, emphasizing time on text and frequent reading practice. Consistent time spent reading aloud (by parent or child) might help a child with attention difficulties stay focused on text and allow the parent to reinforce accurate letter-to-sound conversions. This is general good practice for everyone but may be especially helpful for those with attention difficulties. As there currently is not strong evidence that central executive training (e.g., Lumosity) has lasting effects, this paper suggests that we focus on the orthographic conversion processing to reduce difficulties.

Recommendation 2

Each individual carries a unique combination of gifts and difficulties. However, although clinicians in the past identified individual disorders in isolation, researchers and clinicians are recognizing that patterns of problems frequently co-occur and that even if they do not reach clinical levels, these problems can occur on a spectrum and still result in some difficulties. The co-occurrence of ADHD and reading difficulties has long been recognized from the reading difficulty side but not necessarily from the ADHD side. Perhaps, then, too many children with ADHD are slipping through school with undiagnosed and unaddressed reading difficulties. Awareness of the relationship between these two disorders in more parents and teachers can help to create optimal diagnosis and treatment of the individual while the brain is young and plastic and most amenable to change.

References

Centers for Disease Control and Prevention. (n.d.). Attention-deficit/hyperactivity disorder (ADHD): Data & statistics. Retrieved from http://www.cdc.gov/ncbddd/adhd/data.html

Cho, E., Roberts, G. J., Capin, P., Roberts, G., Miciak, J., & Vaughn, S. (2015). Cognitive attributes, attention, and self-efficacy of adequate and inadequate responders in a fourth grade reading intervention. Learning Disabilities Research & Practice, 30(4), 159–170.

Willcutt, E. G., Doyle, A. E., Nigg, J. T., Faraone, S. V., & Pennington, B. F. (2005). Validity of the executive function theory of attention-deficit/hyperactivity disorder: A meta-analytic review. Biological Psychiatry, 57, 1336–1346.

Willcutt, E. G., & Pennington, B. F. (2000). Comorbidity of reading disability and attention-deficit/hyperactivity disorder: Differences by gender and subtype. Journal of Learning Disabilities, 33(2), 179–191.


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