Profile of reading difficulties in children with attention deficit hyperactivity disorder: a literature review

ABSTRACT

Purpose:  to characterize the reading alterations in individuals with attention deficit hyperactivity disorder.

Methods:  PubMed and SciELO platforms from 2006 to 2016 with the keywords "reading" and "attention deficit hyperactivity disorder", with their equivalents in Portuguese, were searched.

Results:  seven hundred ninety articles were found in the two databases, of which 119 were relevant. After a full reading, twenty five articles were selected for the analysis, according to relevance and other exclusion/inclusion criteria. In 21 of the studies, individuals with attention deficit hyperactivity disorder presented worse performance in reading, as compared with their peers. Of these, 14 studies identified a delay in some skills that are important for reading: processing speed, reading accuracy, phonological awareness, comprehension and/or orthographic processing.

Conclusion:  these results corroborate other studies that have verified the presence of a deficit in academic performance, especially in reading skills, in individuals with attention deficit hyperactivity disorder, that may persist in their adulthood.

Keywords: Reading; Attention deficit hyperactivity disorder; Language

RESUMO

Objetivo:  caracterizar as alterações de leitura presentes em indivíduos com Transtorno do Déficit de Atenção e Hiperatividade.

Métodos:  foram realizadas buscas de publicações nas plataformas PubMed e SciELO de 2006 a 2016 com as palavras-chaves “leitura” e “transtorno do déficit de atenção e hiperatividade”, com seus equivalentes em inglês.

Resultados:  foi encontrado 790 artigos nas duas bases de dados, nas quais 119 eram mais relevantes. Vinte e cinco artigos foram selecionados para a análise, de acordo com a relevância e outros critérios de exclusão/inclusão. Em 21 publicações os indivíduos com Transtorno do Déficit de Atenção e Hiperatividade apresentaram pior desempenho em leitura, comparando com seus pares. Desses, 14 estudos identificaram atraso em algumas habilidades relevantes para a leitura: velocidade de processamento, precisão de leitura, consciência fonológica, compreensão e/ou processamento ortográfico.

Conclusão:  estes resultados corroboram outros estudos que verificaram a presença de déficits nas habilidades de leitura em indivíduos com Transtorno do Déficit de Atenção e Hiperatividade que podem permanecer até a fase adulta.

Descritores: Leitura; Transtorno do Déficit de Atenção e Hiperatividade; Linguagem

Introduction

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by a persistent pattern of inattention, hyperactivity and impulsivity, not expected in typical development, according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-V)¹.

Different studies, especially with twins, have shown the presence of genetic inheritance in ADHD². Genetic vulnerability to ADHD appears to be mediated by several small-effect genes, but further studies are needed to precisely identify what these effects are, as well as which phenotypes are specific for subtypes and comorbidities of the disorder³.

In respect of the biological aspects, some studies have shown that individuals with ADHD present a possible failure in the activation of the striated nucleus, a brain region with a high concentration of dopamine linked to the reward system. In one study, individuals in a control group had striated nucleus activation and dopamine release as soon as they were told about a reward, while individuals with ADHD had the release only after actually receiving it. This delay in reward circuit response may explain the inattention and impulsivity present in individuals with ADHD⁴. These characteristics persist in adolescence and adulthood, but may be less pronounced⁵.

ADHD may be accompanied by comorbidities, the most frequent being written language disorders that appear in 14% of children with ADHD. These findings highlight the importance of the attentional factor in relation to the domain of the language, and emphasize the importance of attention for any type of learning.

In many cases of ADHD, the family and school only refer children to specialists when they are already behind in terms of school performance. Therefore, it is important to look out for reading and writing difficulties that may be due to the inattention, impulsivity or hyperactivity that are associated with ADHD. As the symptomatology of ADHD can affect several areas that impair school performance, it is necessary to identify how this can have an impact on the specific skills necessary for the good development of reading and writing. It is, therefore, important to include both oral and written language assessments to complete the performance profile and assist in the diagnosis of ADHD. This study aimed to identify, through a review of the literature, the reading disorders present in children with ADHD in order to better inform professionals from different areas, as well as to qualify the process of evaluation and intervention for children and adolescents with ADHD. In addition, it was intended to verify the hypothesis that as a result of the attention deficit, there may be decoding errors due to excessive reading guess, reading fluency deficits, which consequently affect reading comprehension.

Methods

PubMed and SciELO databases were searched for articles published between 2006 and 2016 in Portuguese or English, using a combination of the terms "leitura" and "Transtorno do Deficit de Atenção e Hiperatividade (TDAH)" and their equivalents in English, "reading" and "attention deficit hyperactivity disorder (ADHD)”. The databases were selected for their thematic scope and for including open access articles. The search was performed using the advanced search function in both databases, with items classified by relevance, according to the criteria of the database chosen. The choice to only include articles published in Portuguese and English was based on the idea that any scientific community should have access to articles published in their own language, as well as those published in English, the access language of international science.

Selection Criteria

The selection criteria were complete, original articles, published between the years 2006 and 2016, published in Portuguese or English. General studies on ADHD with specific reading disorders as comorbidities were included. Duplicate articles, articles not relevant to the subject, reviews, genetic studies, studies with illiterate/pre-school subjects, case studies, treatment studies, and surveys containing other comorbidities were excluded. Table 1 shows the excluded articles.

Data Analysis

Initially, the first 100 articles were selected according to relevance in each database. The first inspection for the criteria was based on the reading of the titles and abstracts of articles with open access. All duplicate articles were excluded as well as those that did not meet established selection criteria. The same procedure was done for articles with restricted access. When there was doubt about the exclusion criteria, a second judge analyzed the article. The author and the advisor of this study were considered the judges for the inclusion or exclusion of the articles. Upon completion of the collection of the database for analysis, all articles were read completely in order to record all relevant details for further analysis. The studies were organized by journal, year of publication, age of population studied, diagnosis, language spoken, the main purpose of the study, the experimental approach, measures used, and conclusions. For the present study, it focused on the discussion of participants' reading characteristics.

Literature Review

From the survey of the literature, 790 articles were found (771 in PubMed and 19 in Scielo), of which the 100 most relevant were selected from PubMed and all 19 from Scielo.

After reading the titles and abstracts we selected 34 articles for the complete analysis. A summary of the selection process is shown in Figure 1.

Figure 1:
Organization Chart used for the Systematic Review Process

Exclusion and inclusion criteria were used to select the articles. The ones excluded were duplicates or did not fit in the criteria. Review articles or Case reports were also excluded. Table 1 shows the articles excluded.

Table 1:
Distribution of articles excluded according to the exclusion criterion

Category	PubMed	Scielo	Total
Restricted access	2	0	2
Duplicate	3	1	4
Case report	0	1	1
Genetics	8	0	8
Language	4	2	6
Non related with the topic	48	9	57
Literature review	2	1	3
Other psychiatric/neurologic disorders	4	0	4
Preschoolers/illiterates	2	0	2
Treatment	6	1	7
Total	79	15	94

Examining the geohistorical distribution of the articles, in terms of the year of publication, country of origin and language of the publication, may help to understand the interest in this area of research around the world in recent years. Most of the studies analyzed were published in the last 3 years (2014 to 2016) of the period investigated. Of the 25 articles, 6 (24%) were published in 2016, 4 (16%) were published in 2015, 6 (24%) in 2014, 4 (16%) in 2013, 1 in 2012 (4%), 3 (12%) in 2011, and 1 (4%) in 2008. Most of the studies were conducted in the United States of America (10), followed by Brazil (5), Germany (2), Australia (2), Canada (2), Israel (2), Belgium (1) and Spain (1). Of the 25 articles, 21 (84%) were published in English and 4 (16%) in Portuguese.

Figures 2 and 3 show details of each study such as date of publication, authorship, country, goal of the study, sample description, and main findings of the 25 studies analysed^6-30.

Figure 2:
Identification and description of the selected articles, in chronological order of publication

Figure 3:
Sample characterization and results of changes in written language, according to the chronological order of publication

The academic deficits present in ADHD may persist until adult life, even if reduced in severity or the associated symptoms are controlled, as demonstrated in the research of Voigt et al.⁶. The study conducted by Whipple and Nelson⁷, which also included and tracked the performance of adults, showed difficulty in naming tasks in both the ADHD group and the comorbid group. These data are compatible with other findings that report that the incidence rate of ADHD symptoms in adults who showed symptoms in childhood is between 30 and 70%, with the same difficulties persisting in respect of academic performance⁸.

Most of the studies found and analyzed showed that individuals with ADHD had worse academic performance compared to their peers. This data corroborates other studies³¹ that evaluated the academic performance of children without ADHD, with ADHD and, with ADHD and a concomitant learning disorder, and identified performance deficits, especially in reading and writing, both in the ADHD+learning disorder group and in the group with only ADHD ^20-23.

Deficits in Phonological and Orthographic Processing Skills

Among all the studies selected for review, 2 articles showed significant differences between individuals with ADHD and their control group pairs in phonological awareness tasks. In one study, the ADHD group with no comorbidity had a worse performance in phonological awareness, and in the other study, only the group with ADHD and with a specific learning disorder as comorbidity had worse performance in phonological awareness compared to the non-ADHD , and ADHD without learning disorder groups.

There was 1 article with a study in respect of orthographic processing in individuals with ADHD. This study reported that individuals with ADHD demonstrated worse performance in rules knowledge and in orthographic memory. None of the participants in the ADHD group had a specific learning disorder as a comorbidity.

Changes in phonological awareness and orthographic rules are often more severe in learning disorders than in ADHD, due to the presence of common phonological and orthographic processing deficits in individuals with reading disorders. Considering that the development of this ability depends on stimulation and correct learning from the preschool stage, it is not uncommon for children with ADHD to present deficits in phonological and orthographic processing as a possible consequence of the presence of ADHD symptoms, such as inattention and impulsivity^9,13.

Deficit in Reading Performance

Regarding the analysis of reading performance, the majority of the studies showed that there was a significant difference in performance in reading tasks between children with ADHD and the control group (Table 2). Twenty-one studies (84%) found that individuals with ADHD, with or without reading difficulty as a comorbidity, performed significantly worse in reading tests compared to their non-ADHD peers. The other studies analyzed did not find significant differences in the reading performance of children with ADHD or did not aim to identify the reading profile in this group, although they did examine academic performance.

Table 2:
Study summaries according to the reading skills investigated

Related Reading Skills	Number of studies
Word reading rate	9
Word reading accuracy	9
Pseudoword reading rate	3
Pseudoword reading rate	3
Phonological awareness	2
Comprehension (passage, texts)	6
Orthographic processing	3

Of the 21 publications whose results showed poor reading performance in subjects with ADHD, 14 specified different reading-related skills and their characterization in subjects with ADHD. Twelve studies showed a worse performance, specifically in fluency and accuracy of word reading and 3 studies showed worse performance related to pseudoword fluency and accuracy.

The area that showed the greater deficits in the groups with ADHD or groups with a comorbidity (ADHD and learning disabilities) were speed and accuracy of reading^6,7,9-17. Fluency and reading accuracy are important elements, since they allow monitoring of possible changes in the development of reading³². These results are compatible with other studies¹⁹ that showed reduced speed of reading of words and of non-words in individuals with ADHD.

The understanding of texts, passages, and online comprehension was worse in ADHD groups with or without comorbidity of learning disorder, as shown in six studies^{9,11,16,20-22}. The symptoms of individuals with ADHD, such as impulsivity, deficit in inhibitory control, hyperactivity, along with the difficulties in reading present seem to interfere indirectly in reading comprehension, although the etiology of comprehension difficulties in ADHD is not very clear16. This study showed deficits in different aspects of reading comprehension (textual, sentential, inferential) in individuals with ADHD.

Conclusion

The present study aimed to characterize the reading profile of children with ADHD and identify which abilities are more commonly affected. According to the reviewed literature between 2006 and 2016, these difficulties are present at the phonological level and in orthographic processing, which contribute to difficulties in reading accuracy and fluency, and as a consequence, affect reading comprehension.

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Publication Dates

• Publication in this collection
  Nov-Dec 2018

History

• Received
  24 Apr 2018
• Accepted
  11 Sept 2018