Time Trends in the Comorbid Psychiatric Disorders Among Children and Adolescents With Intellectual Disability in Korea: A Nationwide Study From 2012–2021

Background: Children and adolescents with intellectual disability (ID) frequently experience various comorbid psychiatric symptoms.However, research on the comorbidity of psychiatric disorders in this population remains limited.In this study, we aimed to comprehensively examine the prevalence of psychiatric disorders among children and adolescents with ID in South Korea from 2012 to 2021.Methods: We obtained data from the National Health Insurance Service-National Health Information Database (NHIS-NHID) on individuals aged 2-18 years who were diagnosed with ID (F70-F79.9)between 2012 and 2021.Psychiatric disorders were identified using the following the International Classification of Diseases, 10th Edition codes: attention-deficit/ hyperactivity disorder (ADHD) (F90), autism spectrum disorder (ASD) (F84), language disorder (F80), tic disorders (F95), anxiety disorders (F401-F402, F410-F411, F930-F932), depressive disorder (F32, F33), conduct disorder (F918, F928, F911), and oppositional defiant disorder (ODD) (F913).We analyzed the annual prevalence of comorbid psychiatric disorders.Results: Throughout the study period, males consistently outnumbered females (62.6-65.5% vs. 34.5-37.4%).ADHD had the highest prevalence among psychiatric disorders, increasing from 30.23% in 2012 to 41.77% in 2021.Similar increasing trends were observed for ASD (10.95-15.46%)and depression (10.46-19.37%).Significant sex differences were observed in most disorders: ADHD, ASD, tic disorders, language disorder, conduct disorder, and ODD showed male predominance (P < 0.001), while depressive disorder showed female predominance (P < 0.01).Anxiety disorders showed no significant sex differences. Conclusion:This study enhances our understanding of the epidemiology of psychiatric comorbidities in South Korean children and adolescents with ID.The evaluation of comorbid psychiatric disorders in this population is crucial for prognosis, with particular attention needed for ADHD and depressive disorder due to their relatively high prevalence.Future research should focus on preventing and treating psychiatric comorbidities in children and adolescents with ID.