Executive dysfunction is a common feature in both Autism Spectrum Disorder (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD), contributing to the overlap in symptoms between the two conditions.
However, the specific patterns of executive function deficits may differ. In ASD, cognitive inflexibility and planning difficulties are more prominent, while in ADHD, impairments in response inhibition and sustained attention are more characteristic.
Response inhibition is the ability to suppress or withhold inappropriate or irrelevant responses, allowing for flexible and goal-directed behavior.
When ASD and ADHD co-occur, the executive function deficits may be additive.
Lee, K., Cho, I. H., Park, J., Choi, H., & Cheon, K. A. Response inhibition as a critical executive function in differentiating attention-deficit/hyperactivity disorder from autism spectrum disorder: a comprehensive attention test study. Frontiers in Psychiatry, 15, 1426376. https://doi.org/10.3389/fpsyt.2024.1426376
Key Points
- The study aims to elucidate differences in executive function (EF) endophenotypes between Autism Spectrum Disorder (ASD), Attention-Deficit/Hyperactivity Disorder (ADHD), and their co-occurring condition (ASD+ADHD) using the comprehensive attention test (CAT).
- Both the ASD+ADHD and ADHD groups exhibited significantly higher commission errors (CE) and perseveration errors (PE) compared to the ASD group, suggesting that impaired response inhibition is more pronounced in ADHD than ASD.
- The ASD+ADHD group showed a trend of higher standard deviation of reaction time (RTSD) compared to the ASD group, indicating an additive pathology in sustained attention when ASD and ADHD co-occur.
- The exploratory analysis revealed that social difficulties and externalizing symptoms are associated with impaired response inhibition in ADHD but not in ASD, suggesting that cognitive inflexibility may be a more significant EF characteristic in ASD.
Rationale
ASD and ADHD are distinct neurodevelopmental disorders with overlapping features, leading to diagnostic confusion and hindering symptom alleviation (Antshel et al., 2016).
Previous studies have attempted to identify EF features that may differentiate ASD and ADHD as potential endophenotypes, but the findings have been inconsistent (Craig et al., 2016; Antshel & Russo, 2019; Townes et al., 2023).
This inconsistency likely stems from small sample sizes, evolving diagnostic criteria, and heterogeneity of EF measurement tasks between studies (Craig et al., 2016; Antshel & Russo, 2019; Townes et al., 2023).
The current study aims to elucidate specific comprehensive attention test (CAT) characteristics within clinical groups of ASD, ADHD, and ASD+ADHD to evaluate differences in the EF endophenotypes between these two neurodevelopmental conditions using a large clinical sample and a uniform computerized test.
Method
The study utilized retrospective data obtained through a review of electronic medical records of patients treated at the Department of Child and Adolescent Psychiatry at Severance Hospital, Seoul, South Korea.
A total of 371 patients aged 6 to 15 years diagnosed with ASD, ASD+ADHD, or ADHD based on DSM-5 criteria were included in the final analysis.
The participants were divided into three groups: ASD (n=112), ASD+ADHD (n=155), and ADHD (n=104).
The study compared CAT measures among the three groups and conducted an exploratory analysis to examine the association between psychometric variables and CAT measures.
Procedure
Participants completed the CAT, which included four subtests: Visual selective attention test (VA), Auditory selective attention test (AA), Sustained attention to response task (SAR), and flanker test (FT).
The variables included in the analysis for each subtest were omission error (OE), commission error (CE), reaction time (RT), standard deviation of reaction time (RTSD), and perseveration error (PE).
Sample
The study included 371 children aged 6 to 15 years diagnosed with ASD (n=112; mean age 8.06; 83% males), ASD+ADHD (n=155; mean age 8.12; 88.4% males), or ADHD (n=104; mean age 7.36; 78.8% males).
The proportion of males was higher in the ASD and ASD+ADHD groups compared to the general population.
Measures
The study used the CAT to assess EF.
Several parent-reported scales were also implemented, including Korean ADHD rating scales (K-ARS), Korean version of childhood autism rating scale (CARS), Korean version of social communication questionnaire (SCQ), Korean version of social responsiveness scale (SRS), and Korean version of child behavior checklist (CBCL).
Statistical measures
Non-parametric methods (Kruskal-Wallis test and Mann-Whitney test with FDR correction) were used for group comparisons of CAT measures.
Multivariate linear regression analysis was performed for the exploratory analysis, with age, sex, and FSIQ as control variables.
Results
The ASD+ADHD and ADHD groups exhibited significantly higher CE and PE compared to the ASD group in VA, AA, and SAR subtests.
The ASD+ADHD group showed a trend of higher RTSD compared to the ASD group in AA and SAR subtests.
The exploratory analysis revealed that SCQ and CBCL-externalization scores were negatively associated with RT in the ASD+ADHD and ADHD groups but not in the ASD group.
Insight
The study suggests that impaired response inhibition, as evidenced by higher CE and PE on the CAT, is more pronounced in ADHD than ASD and may serve as an endophenotypic marker differentiating ADHD from ASD.
The increased RTSD in the ASD+ADHD group indicates an additive pathological effect on sustained attention when both conditions co-exist.
The exploratory analysis suggests that social difficulties and externalizing symptoms are associated with impaired response inhibition in ADHD, while in ASD, these difficulties may be more closely linked to cognitive inflexibility or other distinct features.
Strengths
The study had several methodological strengths, including a large sample size, a uniform computerized test (CAT), and the inclusion of a co-occurring (ASD+ADHD) group, which enhanced its statistical power and clinical relevance.
Limitations
The study had some limitations, including its cross-sectional design, reliance on data from a single urban tertiary hospital, minor but statistically significant age differences between groups, lack of a typically developing control group, and exclusion of individuals with intellectual disabilities.
These limitations may affect the generalizability of the findings.
Implications
The findings have implications for clinical practice and future research.
Clinicians can use the CAT or other computerized tests to gain more comprehensive insights into a patient’s EF profile, aiding in diagnostic differentiation and guiding intervention strategies.
Future research should aim to integrate these endophenotypic findings with genetic and neurobiological markers in a prospective setting to enhance our understanding of the underlying pathologies of both conditions.
References
Primary reference
Lee, K., Cho, I. H., Park, J., Choi, H., & Cheon, K. A. Response inhibition as a critical executive function in differentiating attention-deficit/hyperactivity disorder from autism spectrum disorder: a comprehensive attention test study. Frontiers in Psychiatry, 15, 1426376. https://doi.org/10.3389/fpsyt.2024.1426376
Other references
Antshel, K. M., & Russo, N. (2019). Autism spectrum disorders and ADHD: Overlapping phenomenology, diagnostic issues, and treatment considerations. Current psychiatry reports, 21, 1-11. https://doi.org/10.1007/s11920-019-1020-5
Craig, F., Margari, F., Legrottaglie, A. R., Palumbi, R., De Giambattista, C., & Margari, L. (2016). A review of executive function deficits in autism spectrum disorder and attention-deficit/hyperactivity disorder. Neuropsychiatric disease and treatment, 1191-1202. https://doi.org/10.2147/NDT.S104620
Townes, P., Liu, C., Panesar, P., Devoe, D., Lee, S. Y., Taylor, G., … & Schachar, R. (2023). Do ASD and ADHD have distinct executive function deficits? A systematic review and meta-analysis of direct comparison studies. Journal of Attention Disorders, 27(14), 1571-1582. https://doi.org/10.1177/10870547231190494
Keep Learning
- How can the findings of this study inform clinical practice and guide intervention strategies for individuals with ASD, ADHD, or their co-occurring condition?
- What are the potential implications of the observed endophenotypic differences between ASD and ADHD for our understanding of the underlying neurobiological mechanisms of these disorders?
- Given the limitations of this study, what steps can future research take to further validate and expand upon these findings?
- How might the integration of endophenotypic, genetic, and neurobiological markers in prospective studies advance our understanding of the pathologies and potential treatments for ASD and ADHD?
