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Exploring the cognitive and neurostructural profiles of co-occurring developmental dyslexia and ADHD in Chinese children
Poster Session F, Friday, October 2, 2:45 - 4:45 pm, Wangari Maathai
Hanyong Tian1, Jie Chen1, Ningxin Zhao1, Zihan Yang1, Xiujie Yang1; 1Beijing Normal University, Beijing, China
Developmental dyslexia (DD) and attention-deficit/hyperactivity disorder (ADHD) frequently co-occur, yet the mechanisms underlying their comorbidity remain debated. To address whether comorbid DD-ADHD represents a distinct cognitive subtype with more severe deficits (cognitive subtype hypothesis) or a simple additive combination of single-disorder deficits (multiple deficit hypothesis), this study investigated both cognitive skills and gray matter volume (GMV) in Chinese children. In Study 1, we assessed 153 school-aged children (M age = 9.38, SD age = 1.22, 41 typically developing [TD], 38 DD, 32 ADHD, and 42 comorbid) across 9 cognitive skills spanning metalinguistic awareness and executive functions. The comorbid group exhibited more severe deficits in visual working memory, phonological working memory, and morphological awareness relative to the single-disorder groups, while showing comparable deficits to the respective single-disorder groups in phonological awareness, orthographic awareness, rapid automatized naming (RAN), inhibitory control, and cognitive flexibility. In Study 2, we performed whole-brain voxel-based morphometry (VBM) on T1-weighted MRI data from 136 children (M age = 9.74, SD age = 1.42, 48 TD, 37 DD, 31 ADHD, and 20 comorbid) in order to identify the neurostructural profiles. A one-way ANCOVA model controlling for age, IQ, and total intracranial volume (TIV) identified five significant clusters exhibiting group differences. Pairwise post-hoc comparisons revealed distinct neurostructural patterns: Firstly, in the bilateral cingulate cortex and left anterior cingulate cortex (peak MNI: [4, -9, 40], cluster size = 669 voxels), the comorbid group exhibited significantly smaller GMV compared to both the DD (p < .001) and ADHD (p = .021) groups. This suggests that the comorbidity is associated with more severe neurostructural impairments in this region. Secondly, in the left superior frontal gyrus (peak MNI: [-21, 68, -8], cluster size = 539 voxels) and left caudate nucleus (peak MNI: [-9, 16, 10], cluster size = 633 voxels), all three disorder groups showed comparable GMV reductions relative to the TD group (ps < .050). Thirdly, In the left thalamus (peak MNI: [-16, -10, 6], cluster size = 941 voxels) and right thalamus (peak MNI: [15, -26, 14], cluster size = 1072 voxels), both the DD (ps < .047) and comorbid (ps < .032) groups showed comparable GMV reductions relative to the TD group, whereas the ADHD group showed no such deficit (ps > .277).Taken together, these behavioral and structural neuroimaging findings indicate that the deficit profile of DD-ADHD comorbidity is characterized by both specific and shared features. This suggest that the cognitive subtype and multiple deficit hypotheses are complementary rather than mutually exclusive. Specifically, the multiple deficit hypothesis clarifies the origin of comorbid deficits, whereas the cognitive subtype hypothesis identifies more severe deficits that can serve as potential targets for diagnosis and intervention. Consequently, integrating both perspectives in future research will facilitate a more comprehensive understanding and provide a more effective support for children with DD-ADHD comorbidity.
Topic Areas: Disorders: Developmental,