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Background: Autism and attention deficit hyperactivity disorder (ADHD) are heterogeneous neurodevelopmental conditions with complex underlying neurobiology. Despite overlapping presentation and sex-biased prevalence, autism and ADHD are rarely studied together, and sex differences are often overlooked. Normative modelling provides a unified framework for studying age-specific and sex-specific divergences in neurodivergent brain development. Methods: Here we use normative modelling and a large, multi-site neuroimaging dataset to characterise cortical anatomy associated with autism and ADHD, benchmarked against models of typical brain development based on a sample of over 75,000 individuals. We also examined sex and age differences, relationship with autistic traits, and explored the co-occurrence of autism and ADHD (autism+ADHD). Results: We observed robust neuroanatomical signatures of both autism and ADHD. Overall, autistic individuals showed greater cortical thickness and volume localised to the superior temporal cortex, whereas individuals with ADHD showed more global effects of cortical thickness increases but lower cortical volume and surface area across much of the cortex. The autism+ADHD group displayed a unique pattern of widespread increases in cortical thickness, and certain decreases in surface area. We also found evidence that sex modulates the neuroanatomy of autism but not ADHD, and an age-by-diagnosis interaction for ADHD only. Conclusions: These results indicate distinct cortical differences in autism and ADHD that are differentially impacted by age, sex, and potentially unique patterns related to their co-occurrence.
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ImportanceHeterogeneous mental health outcomes during the COVID-19 pandemic are recognized in the general population, but it has not been systematically assessed in youth with neurodevelopmental disorders (NDD), including autism spectrum (ASD). ObjectiveIdentify subgroups of youth with ASD/NDD based on the pandemic impact on symptoms and service changes, as well as predictors of outcomes. Design, Setting, and ParticipantsThis is a naturalistic observational study conducted across 14 North American and European clinical and/or research sites. Parent responses on the Coronavirus Health and Impact Survey Initiative (CRISIS) adapted for Autism and Related Neurodevelopmental Conditions (AFAR) were cross-sectionally collected from April to October 2020. The sample included 1275, 5-21 year-old youth with ASD and/or NDD who were clinically well-characterized prior to the pandemic. Main Outcomes and MeasuresTo identify impact subgroups, hierarchical clustering analyzed eleven AFAR factors measuring pre- to pandemic changes in clinically relevant symptoms and service access. Random forest classification assessed the relative contribution in predicting subgroup membership of 20 features including socio-demographics, pre-pandemic service, and clinical severity along with indices of COVID-19 related experiences and environments empirically-derived from AFAR parent responses and global open sources. ResultsClustering analyses revealed four ASD/NDD impact subgroups. One subgroup - broad symptom worsening only (20% of the aggregate sample) - included youth with worsening symptoms that were above and beyond that of their ASD/NDD peers and with similar service disruptions as those in the aggregate average. The three other subgroups showed symptom changes similar to the aggregate average but differed in service access: primarily modified services (23%), primarily lost services (6%), and average services/symptom changes (53%). Pre-pandemic factors (e.g., number of services), pandemic environments and experiences (e.g., COVID-19 cases, related restrictions, COVID-19 Worries), and age emerged in unique combinations as distinct protective or risk factors for each subgroup. Together they highlighted the role of universal risk factors, such as risk perception, and the protective role of services before and during the pandemic, in middle childhood. Conclusions and RelevanceConcomitant assessment of changes in both symptoms and services access is critical to understand heterogeneous impact of the pandemic on ASD/NDD youth. It enabled the delineation of pathways to risk and resilience that include universal and ASD/NDD specific contributors.
