Depression and Anxiety Risk in Children With Intellectual Developmental Disorder.

Importance: Population-based pediatric data on depression and anxiety incidence among children with intellectual developmental disorder (IDD), particularly in Asian populations, are limited. Objective: To investigate associations between IDD and depression and anxiety incidence and evaluate moderating factors. Design, Setting, and Participants: This retrospective cohort study used linked data from South Korea's National Health Insurance Service database and National Disability Registry from 2004 to 2020. Children aged 2 to 17 years with newly registered IDD were matched 1:3 by sex and birth year to children without developmental disorders. Follow-up continued until 2023. Data were analyzed from April 20 to July 9, 2025. Exposure: Intellectual developmental disorder among children and adolescents. Main Outcomes and Measures: The primary outcome was incident depression and anxiety as defined by International Statistical Classification of Disease, Tenth Revision codes. Hazard ratios (HRs) and 95% CIs for developing depression or anxiety were estimated using multivariable-adjusted Cox proportional hazards regression models. Results: Among 236 132 children (mean [SD] age, 9.3 [4.3] years; 64.2% male), 59 033 (25.0%) had IDD. Among children with IDD, 20.1% were diagnosed with depression and 21.9% with anxiety at least 1 year after baseline. Compared with children without developmental disorders, children with IDD had higher risk of depression (HR, 2.18 [95% CI, 2.13-2.24]) and anxiety (HR, 1.85 [95% CI, 1.80-1.89]) after adjusting for sex, age, income level, residential location, and comorbidity burden. Compared with children without developmental disorders, risks of depression and anxiety, respectively, were higher among male children (adjusted HR [AHR], 2.46 [95% CI, 2.39-2.54] and 2.06 [95% CI, 2.00-2.12]), younger children (aged 2-5 years: AHR, 2.83 [95% CI, 2.66-3.01] and 2.41 [95% CI, 2.27-2.55]; aged 6-8 years: AHR, 2.51 [95% CI, 2.40-2.64] and 2.12 [95% CI, 2.02-2.22]), urban residents (AHR, 2.36 [95% CI, 2.25-2.48] and 1.97 [95% CI, 1.88-2.06]), and children with a mild comorbidity burden (Charlson Comorbidity Index score of 1) (AHR, 2.32 [95% CI, 2.22-2.43] and 1.98 [95% CI, 1.90-2.07]). Stratification by sex, younger age, and mild comorbidity burden consistently showed higher risks of depression and anxiety across both sexes with IDD compared with children without developmental disorders (all P < .001 for interaction). In males with IDD, rural residence was associated with higher depression risk (AHR, 2.71 [95% CI, 2.56-2.86]) and urban residence with higher anxiety risk (AHR, 2.15 [95% CI, 2.04-2.28]). In females with IDD, depression and anxiety, respectively, were associated with lower income (AHR, 2.08 [95% CI, 1.86-2.34] and 1.76 [95% CI, 1.59-1.96]) and urban residence (AHR, 2.03 [95% CI, 1.88-2.20] and 1.73 [95% CI, 1.62-1.86]). Mild comorbidity burden was associated with increased risks of depression (AHR, 1.18 [95% CI, 1.07-1.31]) and anxiety (AHR, 1.16 [95% CI, 1.06-1.27]) for both sexes. Within the IDD cohort, female sex, older age, and lower income status were associated with higher risks of both outcomes (all P < .001 for trend). Conclusions and Relevance: This nationwide cohort study of more than 236 000 children and adolescents found that individuals with IDD, particularly males, younger children, and those with mild comorbidity burden, had increased depression and anxiety risks compared with individuals without developmental disorders. These findings underscore the need for targeted screening and interventions tailored to sociodemographic and comorbidity profiles.