Summary:
Autism spectrum disorder (ASD) involves difficulties in social communication along with repetitive behaviours and is often accompanied by other conditions such as intellectual disability, ADHD, epilepsy, anxiety, and mood disorders. Many individuals with ASD have at least one additional medical or psychiatric condition. Early diagnosis allows access to intervention and family support, which can improve language, social skills, and adaptive functioning. Differences in diagnosis timing may be influenced by sex, co-occurring conditions, and symptom severity. Previous research has shown that girls are often diagnosed later than boys, possibly due to more subtle behavioural presentations. Intellectual disability tends to be recognised early, while ADHD may delay identification of ASD because overlapping behaviours can make diagnosis less clear. This study, a large observational analysis, examined the relationship between co-occurring psychiatric conditions and age at ASD diagnosis. Clinical data included psychiatric diagnoses, developmental characteristics and medication use. More than 50,000 people with ASD were included. Across two datasets, children with no additional psychiatric diagnoses were identified with ASD at a younger age than those with multiple co-occurring conditions. Age at diagnosis increased as the number of psychiatric conditions increased. Depression and ADHD were linked with later ASD diagnosis, while OCD and intellectual disability were associated with earlier diagnosis. In summary, this study found that children with ASD who have multiple psychiatric conditions are typically diagnosed later, suggesting a potential subgroup of individuals who may require improved screening and tailored clinical approaches.
Abstract:
Purpose: In children with autism spectrum disorder (ASD), early diagnosis permits early access to therapeutic interventions which may improve outcomes. Factors affecting the age of diagnosis in ASD are not fully understood. Methods: Here, two large independent datasets were analyzed to investigate age of autism diagnosis and co-occurring psychiatric conditions, including bipolar disorder, depressive disorder, anxiety disorder, obsessive-compulsive disorder, attention deficit hyperactivity disorder, oppositional defiant disorder, and conduct disorder. Clinical characteristics examined included demographics, verbal status, intellectual disability, restricted/repetitive behaviors, adaptive behaviors, and psychiatric medication use. Results: Over 50,000 participants with ASD were analyzed from the Rhode Island Consortium for Autism Research and Treatment study (RI-CART; n = 823) and the Simons Foundation Powering Autism Research for Knowledge (SPARK) database (n = 52,611). In RI-CART, age of diagnosis differed between those with no co-occurring conditions (mean age at diagnosis = 4.3 years), those with one or two co-occurring conditions (7.1 years), and those with three or more co-occurring conditions (8.5 years; p < .001). This pattern was observed in the SPARK database (age of diagnosis 4, 7.1, and 10 years, respectively; p < .001). Controlling for age, sex, and symptom severity, more co-occurring psychiatric conditions was associated with later age of ASD diagnoses in both samples. Depression and ADHD were associated with later ASD diagnoses; OCD and ID were associated with earlier ASD diagnoses. Conclusion: These findings indicate that those children with high co-occurring psychiatric conditions, who are ultimately diagnosed with ASD, experience later diagnosis. This group of children may represent a distinct subtype of autism.
Article Publication Date: 17/11/2025
DOI: 10.1007/s10803-025-07113-2
