Profiles of Executive Function in Austim Spectrum Disorders and Attention Deficit/Hyperactivity Disorder

Background:  Executive function (EF) impairments are common in many developmental disorders.  However, questions remain as to whether patterns or profiles within executive function subdomains distinguish one disorder from another. For example attention deficit hyperactive disorder (ADHD) has been associated with particular problems with inhibition and working memory, while autism spectrum disorder (ASD) has been linked to problems with flexibility.  Approximately half of children diagnosed with ASD also meet diagnostic criteria or exhibit clinically significant symptoms of ADHD-Combined Type or ADHD-Inattentive Type.

Objectives:  To compare the profiles of EF subdomains in children diagnosed with ADHD-Combined Type (ADHD-C); ADHD-Inattentive Type (ADHD-I); ASD, ASD with comorbid ADHD-C (ASD+ADHD-C), and ASD with comorbid ADHD-Inattentive Type (ASD+ADHD-I).

Methods:  Executive functioning was assessed in a sample of 224 children (166 males, 58 females, age range 5-18 years; mean = 9.8, SD = 2.7) at Children’s National Medical Center, as part of a neuropsychological evaluation or research protocol, with parent ratings of the Behavior Rating Inventory of Executive Function (BRIEF).  The sample included the following clinical diagnostic groups: ASD (n=76), ASD+ADHD-C (n=23), ASD+ADHD-I (n=25), ADHD-C (n=73) and ADHD-I (n=27).  The clinical groups were matched for gender, age and IQ. A repeated measures ANOVA was conducted to evaluate main and interacting effects between diagnostic category and BRIEF subscale (Inhibition, Shift, Emotional Control, Initiation, Working Memory, Planning/Organization, Organization of materials, and Monitor).

Results:  Results revealed a significant main effect of BRIEF subscale (F (7, 1498) =17.930, p < .001), partial eta squared = .077).  Post hoc analysis revealed that among all the diagnostic groups combined, Working Memory (M t-score=67.38) and Shift (M t-score=66.11) showed the greatest impairment, whereas Organization of materials (M=59.41) was least affected.  The main effect of diagnostic group was also significant (F (4,214) = 14.12, p=.000, partial eta squared =. 209).  Post hoc analysis revealed that the ASD and ADHD-I groups where less impaired overall on the BRIEF than the other groups.  Across the BRIEF subscales, comorbid ASD+ADHD-C demonstrated the most executive dysfunction, followed by ASD+ADHD-I, particularly on the Shift, Working Memory, and Plan/Organize subscales. A significant interaction effect between the diagnostic groups and the BRIEF subscales was also found, (F (28, = 6.089, p=.000, partial eta squared =.102), with unique profiles associates with specific diagnostic groups.

Conclusions:  These findings suggest differences among diagnostic groups in both the severity of parent reported EF problems overall and in specific subdomain profiles, which supports recent changes in the Diagnostic and Statistical Manual-5 allowing the diagnosis of ADHD with ASD and also indicates a need for targeted treatment methods with in the EF domain.