Response Inhibition in Adults with Autism Spectrum Disorder Compared to Attention Deficit/Hyperactivity Disorder

Abstract

Autism spectrum disorder (ASD) and attention deficit/hyperactivity disorder (ADHD) are hypothesised to involve core deficits in executive function. Previous studies have found evidence of a double dissociation between the disorders on specific executive functions (planning and response inhibition). To date most research has been conducted with children. No studies have directly compared the stable cognitive profile of adults. It was hypothesised that adults with ASD would show generally intact response inhibition whereas those with ADHD would show more global impairment. Participants were 24 adults aged 18-55 with high functioning ASD, 24 with ADHD, and 14 age and IQ matched controls. Participants completed three standardised measures of response inhibition. Participants with ASD had generally intact response inhibition but slow response latencies, possibly due to deficits in response initiation. Adults with ADHD did not show the more global impairments hypothesised. There were some significant differences between the clinical groups across measures of inhibition. In terms of performance style, adults with ASD were slow and accurate whilst those with ADHD showed an impulsive style.

Prefrontal activation during inhibitory control measured by near-infrared spectroscopy for differentiating between autism spectrum disorders and attention deficit hyperactivity disorder in adults

“…The only neuropsychological study performed in adult patients revealed significant differences between ADHD and ASDs in the Stroop task. However, using the Hayling Sentence Completion Test, which assesses verbal response inhibition, it was found that adults with ADHD did not exhibit more severe impairments compared to those with ASDs (Johnston et al, 2011). …”

Inhibition in Autism: Children with Autism have Difficulty Inhibiting Irrelevant Distractors but not Prepotent Responses

“…Another important point to note is that all but two (Iarocci and Burack 2004;Ozonoff and Strayer 1997) of the above studies reporting unimpaired inhibition in participants with autism employed prepotent response inhibition tasks in which participants have to withhold an inappropriate response that is prompted by a target stimulus (see also Johnston et al 2011). In contrast, studies that have examined resistance to distractor inhibition, in which participants have to ignore competing distractors while attempting to focus on a separate target stimulus, have tended to show clearer evidence of difficulties among individuals with autism.…”

Event-Related Potential Study of Attention Regulation During Illusory Figure Categorization Task in ADHD, Autism Spectrum Disorder, and Typical Children

“…Gargaro et al (2011) surmise that when using independent domains of executive functions, children with autism and those with ADHD exhibit opposite patterns (see also Pennington & Ozonoff, 1996). A recent study in adults similarly revealed potential dissociable features of executive functions between ADHD and ASD based on the Stroop, Matching Familiar Figures (MFF), and the Hayling sentence completion tests (Johnston, Madden, Bramham, & Russel, 2011). Not surprisingly, these authors conclude that evidence derived from executive functions assessments remains inconclusive and that further studies are needed (Gargaro et al, 2011; Johnston et al, 2011).…”