Parent, Teacher and Self-Report of Behavioral and Adaptive Functioning in Youth with ADHD and ASD

Background: Autism spectrum disorder (ASD) and attention deficit / hyperactivity disorder (ADHD) are common neurodevelopmental disorders which share some similar symptoms of social, emotional, and attention deficits. Once considered an exclusionary criterion for ADHD, there is now compelling evidence that behavioral characteristics of ADHD are observed in a large proportion of individuals with ASD. While much data have been published about ADHD and ASD individually, far less data have been published about the comorbid state (ASD+ADHD) and those data that have been published have been plagued by a lack of information about school behavior and functioning as well as small sample sizes. Thus, large scale efforts to investigate ASD+ADHD that include teacher report are sorely needed, especially an investigation of how the comorbid state compares to ASD and ADHD in isolation. 

Objectives: The current investigation is a descriptive study comparing parent, teacher and self-reported behavior and functioning in three groups of children and adolescents: youth with ADHD, youth with high levels of ASD symptoms and youth with ADHD+high levels of ASD symptoms. Rather than assess a dichotomous ASD diagnosis, a decision was made to consider a Research Domain Criteria (RDoC) framework for high levels of ASD symptoms using the RDoC domain of Social Communication. 

Methods: Participants were recruited from several large outpatient child and adolescent psychiatry specialty clinics housed within an urban academic medical center. Each participant for the current study received a rigorous psychiatric diagnosis made with the Kiddie-Sads-Present and Lifetime Version (K-SADS-PL) for the ADHD cohorts and the Autism Diagnostic Interview - Revised (ADI-R) for the high levels of ASD symptom cohorts. Participants consisted of 364 youth with ADHD alone, 81 children with high levels of ASD symptoms alone, and 38 children with a clinical diagnosis of ADHD and a high level of ASD symptoms. The Behavior Assessment System for Children – 2^nd edition (BASC-2) parent, teacher and self-report measures served as the primary outcome measure. 

Results: With regard to behaviors, the profile of ratings were generally consistent between parents and teachers and were significant for an externalizing disorder profile with ADHD cohorts and an internalizing disorder profile within the ASD symptoms cohorts. Children in all three groups self-reported less behavioral symptoms than adults. With regard to functioning, the parent and teacher data suggest a linear relationship between the three groups: the ADHD group was rated as the least impaired and the ADHD+ASD symptoms group was rated as the most impaired.  

Conclusions: Careful clinical evaluation for the presence of ASD symptoms in individuals with ADHD (and vice versa) is recommended. ADHD is associated with an externalizing profile in youth with high levels of ASD symptoms. This is consistent with ADHD in the non-ASD population. The comorbid state was the most functionally impaired. This finding suggests that treatments designed to intervene with this common comorbid state represent a clinically significant line of investigation.