Prevalence of and factors associated with multiple neurodevelopmental disorders among children and adolescents: a nationwide cross-sectional study.

OBJECTIVES: Multiple neurodevelopmental disorders (NDDs) in children and adolescents are associated with greater impairment and reduced responsiveness to standard treatments, yet their prevalence and associated factors remain poorly understood. We aimed to investigate prevalence of, and factors associated with multiple NDDs among children and adolescents in the United States (US). METHODS: This nationwide cross-sectional study used data from the National Survey of Children's Health 2016-2023. Multiple NDDs were defined as the concurrent presence of two or more conditions. Weighted prevalence estimates were calculated, and logistic regression was applied to assess associated factors of multiple NDDs adjusting for sociodemographic and health variables. RESULTS: The prevalence of multiple NDDs among children aged 3-17 years increased from 5.8% in 2016 to 7.7% in 2023, with the strongest cross-sectional association observed for depression or anxiety (aOR = 5.53, 95% CI: 5.09-6.02), followed by fair or poor health (aOR = 2.82, 95% CI: 2.33-3.42), heart conditions (aOR = 1.93, 95% CI: 1.59-2.35), underweight status (aOR = 1.30, 95% CI: 1.13-1.50), and allergies (aOR = 1.17, 95% CI: 1.08-1.26). Lower odds were observed among female children (aOR = 0.40, 95% CI: 0.37-0.43) and those with higher parental education (aOR = 0.86, 95% CI: 0.80-0.93). CONCLUSION: This study revealed a rising prevalence of multiple NDDs and identified associated factors across clinical, demographic, and socioeconomic domains. Although the cross-sectional design precludes temporal or causal inference, the findings highlight the importance of integrated and equity-driven strategies to ensure timely access to health services and family-centered support for children and adolescents with multiple NDDs.