Age at first autism spectrum disorder diagnosis: the role of birth cohort, demographic factors, and clinical features

Abstract

Objective: This study sought to identify factors that may be associated with delays in autism spectrum disorder (ASD) diagnosis, including birth cohort, sociodemographic characteristics, and clinical features.

Methods: Participants included 1716 children and adolescents with ASD enrolled in the Autism Speaks Autism Treatment Network (AS-ATN) between the years 2008 and 2011. Data were collected at enrollment using AS-ATN parent- and clinician-report forms and standardized measures of I.Q., ASD symptoms, adaptive function, and psychiatric symptoms.

Results: Age at first ASD diagnosis was positively correlated with current age, suggesting a birth cohort effect. Sociodemographic and clinical features were also associated with age at diagnosis, even after controlling for current age. Hierarchical linear regression results showed that older current age, lower socioeconomic status (SES), higher I.Q. score, and lower levels of autism symptoms were associated with later age at initial diagnosis. There was also a significant interaction between current age and I.Q., with higher functioning children being diagnosed at younger ages than in previous years.

Conclusions: Early diagnosis of ASD is critically important for improving access to interventions; however, many children experience diagnostic delays. In this sample, children from the most recent birth cohorts were diagnosed earlier, suggesting that early signs of ASD are being increasingly recognized. However, socioeconomic barriers to diagnosis still seem to exist. Children with less severe ASD symptoms and with higher I.Q. are also diagnosed at later ages. Efforts are still needed to reduce diagnostic disparities for families of low SES and to improve early recognition of more subtle symptoms.