The reading difficulties in Chinese for individuals with attention deficit hyperactivity disorder: the role of executive function deficits

Ethics statement

The study protocol was reviewed and approved by the Ethics Committee of Ningbo Kangning Hospital (approval No. NBKNYY-2020-LC-50, 12 August 2021). All procedures conformed to the Declaration of Helsinki. Parents or legal guardians provided written informed consent after receiving a detailed description of study aims, potential risks (e.g., possible emotional distress when answering reading-difficulty items), and confidentiality limits, including the hospital’s mandatory-reporting policy. Child participants gave written or oral assent in age-appropriate language. All questionnaires were completed anonymously; datasets were de-identified, stored on an encrypted drive, and shared only in aggregate form.

Study design

We employed a cross-sectional design to compare executive-function (EF) profiles and Chinese reading abilities between two subgroups of children with ADHD: (i) ADHD-only and (ii) ADHD + RD. Data collection was carried out from 1 September 2021 to 30 September 2023. Figure 1 presents the recruitment and allocation flow.

Participants

A total of 212 consecutive patients aged 6–16 years who attended the Children and Adolescent Psychiatry Clinic, Ningbo Kangning Hospital, were screened. Inclusion criteria were: (1) Diagnosis of ADHD confirmed by two licensed child psychiatrists according to DSM-5; (2) Full-scale IQ ≥ 70 (WISC-IV Chinese version); (3) Normal or corrected-to-normal vision and hearing; (4) No ADHD- or RD-related medication or behavioural intervention in the previous 3 months.

Exclusion criteria comprised: autism spectrum disorder, other major neurodevelopmental disorders, psychotic disorders, neurological disease, or uncorrected sensory deficits. Thirty-two children were excluded (17 did not meet IQ criterion; 15 declined participation). The remaining 160 participants were stratified by their Dyslexia Checklist for Chinese Children (DCCC) total score (cut-off ≥ −1 SD) into an ADHD-only group (n = 80) and an ADHD + RD group (n = 80).

Survey content

In order to comprehensively assess the executive function and reading ability of ADHD patients, this study utilized the following measurement tools:

Data analysis methods

After logic checking and proofreading, we used SPSS 23.0 (IBM Corp., Armonk, NY, USA) to process and analyze the data. To comprehensively assess and interpret the research data, the following detailed data analysis methods were employed in this study:

Descriptive statistics: Initially, descriptive statistical analysis was conducted on baseline data for all participants, including intelligence, reading ability, ADHD symptoms, and executive function test results. This involved calculating the mean, standard deviation, minimum, and maximum values to provide an overview of the data distribution.

Independent samples t-test: The independent samples t-test was utilized to compare the differences between the ADHD-along group and the ADHD comorbid with RD group on measures of intelligence (Wechsler Intelligence Scale for Children), total scores, and subscale scores on the Parent-rated Disruptive Behavior Disorder Rating Scale (DBDRS). This analysis method was employed to assess whether there were significant differences in means between the two groups on continuous variables.

Pearson correlation analysis: Pearson correlation analysis was conducted to explore the associations between scores on the DCCC scale and scores on ADHD symptomatology, as well as the accuracy rates of various executive tasks. This analysis aids in identifying linear relationships between reading disability scores and other variables.

Analysis of covariance (ANCOVA): Utilizing ANCOVA, with the DCCC total score as the dependent variable, ADHD total symptom score as the fixed factor, while controlling for age, Wechsler Intelligence Scale for Children (WISC) score, accuracy rates on the VSWM task (2-back), VWM task (0-back, 1-back, 2-back), and response inhibition task. This method helps elucidate the independent effects of single or multiple predictors on the variability of the dependent variable while controlling for other variables.

Significance testing: All statistical tests were set at a significance level of α = 0.05. Appropriate F-statistics and p-values were utilized to report the significance of each factor in the analysis of covariance, ensuring the statistical validity of the results.

Through the comprehensive statistical methods described above, this study aimed to accurately assess the relationship between ADHD and reading disabilities, and delve into how executive function deficits impact the reading ability of ADHD patients. The selection of these methods ensured the scientific rigor of the study results, providing reliable data support for future intervention strategies and treatment recommendations.

Univariate between-group comparative analysis

In this study, we compared the demographic characteristics and various assessment indicators between the ADHD-along group (80 cases) and the ADHD comorbid with reading disabilities (ADHD+RD) group (80 cases), as shown in Table 1. No statistically significant differences were observed between the two groups in terms of gender (81.25% male) and age (mean 9.92 years, standard deviation approximately 1.02). (gender: χ² = 0.00, p = 1.000; age: t = −0.08, p = 0.938). The comparison of SNAP-IV total scores and its subscales (inattention, hyperactivity/impulsivity, oppositional symptoms) also showed no significant differences between the two groups. For instance, the total scores were 36.16 ± 12.41 for the ADHD-along group and 37.20 ± 13.08 for the ADHD+RD group (t = −0.52, p = 0.607).

The ADHD+RD group scored significantly higher than the ADHD-along group on both the total score and all subscales of the dyslexia checklist for Chinese children (DCCC). For instance, there was a significant difference in the total score of the Children’s Chinese Dyslexia Checklist (DCCC) between the pure ADHD group (145.81 ± 36.77) and the ADHD+RD group (177.13 ± 31.62) (t = −5.78, p < 0.001). In the executive function tests, the ADHD+RD group exhibited significantly lower accuracy rates in the VWM task (e.g., 1-back task accuracy: pure ADHD group 0.96 ± 0.05 compared to ADHD+RD group 0.88 ± 0.11, t = 6.17, p < 0.001) and the VSWM task (e.g., accuracy of ADHD-along group 0.88 ± 0.04 compared to ADHD+RD group 0.73 ± 0.09, t = 12.77, p < 0.001), as well as the Go/No-go task (ADHD-along group 0.97 ± 0.02 compared to ADHD+RD group 0.94 ± 0.04, t = 7.13, p < 0.001), compared to the pure ADHD group.

These findings reveal significant differences in the severity of reading disabilities and executive function performance among children with ADHD comorbid with reading disabilities, suggesting that this group faces greater challenges in cognition and executive functioning.

Correlation analysis results

In analyzing the association between ADHD symptoms, executive function performance, and the severity of reading disabilities, we observed some interesting patterns. As shown in Table 2, the correlation results between DCCC scores, ADHD symptoms, and performance on executive function tasks demonstrate significant associations among these variables.

Theoretical implications of the findings

To our knowledge, this is the first study to systematically examine how distinct executive-function (EF) components relate to Chinese reading difficulty in children with ADHD. We found that the ADHD+RD group performed significantly worse than the ADHD-only group on VWM, VSWM and response-inhibition tasks, mirroring the pattern reported by Gooch, Snowling & Hulme (2011) in English readers. Unlike alphabetic scripts, Chinese is morpho-syllabic: characters integrate complex stroke configurations, semantic radicals and only indirect phonological cues (Perfetti & Tan, 1998; McBride, 2016). Reading therefore imposes heavier VSWM and visual-analysis demands and weaker grapheme–phoneme support than English or Spanish (Chung & Lam, 2020). Our data confirm this: deficits in VSWM showed the strongest correlation with DCCC scores (r = −0.42, p < 0.01), highlighting script-specific EF bottlenecks in ADHD-related reading problems. The findings fit a multiple-deficit account (Willcutt et al., 2010): ADHD is genetically linked to inhibition deficits, RD to working-memory deficits; their co-occurrence produces compounded, not merely additive, impairments.

Correlational analyses confirmed that poorer EF scores—especially on the visuospatial task—were moderately associated with greater Chinese reading difficulty. Two script-specific factors may explain why VSWM is particularly salient. First, Chinese characters require holistic visual analysis of complex stroke configurations, placing a higher load on spatial memory than alphabetic decoding (Perfetti & Tan, 1998). Second, phoneme-level mapping is absent; therefore, children must inhibit competing character candidates during recognition, aligning with the observed inhibition deficit.

Genetically, ADHD has been linked to response-inhibition pathways, whereas RD is associated with working-memory loci (Willcutt et al., 2010). Our findings suggest an interactive amplification rather than a linear addition of these vulnerabilities, consistent with twin data showing that the shared variance between reading difficulty and attention problems is largely attributable to the attentional component (Greven et al., 2011). Preliminary neuroimaging work suggests overlap in frontostriatal circuits (e.g., right caudate volume; McGrath & Stoodley, 2019), offering a plausible neural basis that warrants direct testing in future multimodal studies.

Practical implications

Given the strong EF–reading links, intervention should move beyond core ADHD symptoms to include EF-focused training. Randomised trials show that a 6-week visuospatial n-back protocol (20 min, three times per week) improves both VSWM and Chinese character recognition (Lee, 2024). Similarly, stop-signal or Go/No-go gamified drills can enhance response inhibition and sustain attention. In classrooms, visual chunking of stroke patterns and explicit teaching of semantic radicals may reduce VSWM load and accelerate character acquisition.

Furthermore, our findings underscore the importance of individualized interventions for children with ADHD comorbid with RD in clinical practice. For instance, training aimed at enhancing visual spatial working memory and response inhibition abilities may help improve reading skills and attentional control in these children. This is also consistent with the findings of Lee (2024), who observed significant deficits in visual spatial working memory among Chinese children with reading difficulties. The stronger correlation between reading ability and attention deficit symptoms is supported by neuroimaging studies, which have found associations between ADHD and RD and the volume of frontal lobe regions, which are linked to attentional control (Jagger-Rickels, Kibby & Constance, 2018; Kibby et al., 2020, 2021). Based on early developmental studies of large samples of twins, the genetic correlation between reading and attention deficit is significantly greater than that of hyperactivity, indicating that the substantial genetic overlap observed in the symptom domains of ADHD and reading difficulties is largely driven by attention deficits (Greven et al., 2011; Paloyelis et al., 2010).

Strengths and limitations

This study is among the first to link distinct executive-function components to Chinese reading difficulty in children with ADHD, and it does so with a clinically diagnosed sample and well-validated EF tasks. Nevertheless, three limitations should be acknowledged. First, the sample, though carefully screened, is modest in size and drawn from a single outpatient clinic, which may constrain statistical power and generalisability. Second, the cross-sectional design precludes conclusions about developmental trajectories; future longitudinal work could test how executive-function deficits and reading outcomes influence one another over time. Third, reading disability was identified with the parent-rated DCCC alone; although the scale shows strong psychometrics, incorporating an objective measure such as a timed character-recognition or oral-reading-fluency task would provide additional convergent validity. Addressing these issues in larger, multi-site, longitudinal studies—and examining how targeted interventions on visuospatial working memory or response inhibition alter reading progress—will be valuable next steps.

Exacerbation of cognitive impairments

Children with comorbid ADHD and RD exhibit greater difficulties in executive functioning, which are closely linked to the severity of reading disabilities. This indicates that the co-occurrence of ADHD and RD creates a complex neurocognitive profile, necessitating targeted diagnostic and intervention strategies.

Theoretical implications

The study findings support the hypothesis of shared neurobiological pathways or even genetic bases between ADHD and RD, contributing to the observed cognitive impairments. By confirming that these overlaps result in a unique pattern of cognitive deficits different from children with either condition alone, this study extends previous research.

Clinical implications

The findings underscore the importance of developing targeted intervention strategies that address both the core symptoms of ADHD and specific executive function deficits associated with RD. Interventions focused on enhancing visual spatial working memory and improving response inhibition may be particularly beneficial in improving academic performance and daily functioning in children with comorbid ADHD and RD.

Future directions

Despite providing valuable insights, this study is limited by its cross-sectional design and relatively small sample size. Future research should employ longitudinal studies to track cognitive deficits and their impact on ADHD and RD symptoms over time. Additionally, exploring the effectiveness of specific interventions targeting the unique cognitive deficits identified in comorbid ADHD and RD is crucial.

In conclusion, the interdependence between ADHD and RD necessitates consideration of the complex cognitive impairments present in affected children during diagnosis and treatment. As we continue to uncover the genetic and neurobiological basis of these conditions, our clinical strategies must evolve to effectively support this vulnerable population.