A new study published in the Journal of Autism and Developmental Disorders revealed that children and adolescents with Down syndrome (DS) are significantly more likely to be diagnosed with autism spectrum disorder (ASD) and attention deficit/hyperactivity disorder (ADHD), illuminating the complexity of co-occurring developmental conditions.This study analyzed data from the National Health Interview Survey and included 2,14,300 children aged between 3 and 17 years. Among these, 329 children were identified as having physician-diagnosed DS. Within this group, 21 were also diagnosed with ASD, 48 with ADHD, and 6 had co-occurring ASD and ADHD diagnoses.Using logistic regression analysis with adjustments for demographic variables such as age and sex, the study found striking associations. Children with DS were over 5 times more likely to also have autism (odds ratio [OR] = 5.40; 95% confidence interval [CI]: 3.04–9.59) when compared to children without DS. The risk of having ADHD was also elevated (OR = 1.72; 95% CI: 1.17–2.53). For the individuals experiencing both ASD and ADHD, the odds were more than 3 times higher in children with DS (OR = 3.45; 95% CI: 1.29–9.20).The research conducted a sex-stratified analysis to investigate whether boys and girls with DS experienced different rates of comorbidity. The findings indicated that both male and female children with DS were at increased risk for ASD and ADHD, but there was a notable interaction effect between sex and ASD, with statistical significance (P < 0.001). This suggests that the association between DS and autism may manifest differently across genders, though further investigation is needed to understand this disparity.These findings highlight the importance of careful developmental screening in children with DS, as early detection of co-existing conditions like ASD and ADHD can be crucial for timely intervention and support. Despite the clear association demonstrated in this study, the study emphasized the correlation between DS, ASD, and ADHD is not yet fully understood. More research is needed to identify the biological or environmental mechanisms involved.Source:Wang, X., Wang, C., Lin, L., Bao, W., Liu, B., Lin, B., Zhang, L., & Xu, G. (2025). Associations of Down syndrome with autism spectrum disorder and attention deficit/ hyperactivity disorder among children and adolescents. Journal of Autism and Developmental Disorders. https://doi.org/10.1007/s10803-025-06834-8