Cognition in ADHD and Autism

Background: ADHD and Autism are both heterogeneous, lifelong neurobiological developmental disorders, which have an enormous impact on all developmental domains. Recently research regarding the etiology of these neurodevelopmental disorders is increasingly moving towards determining intermediate phenotypes that will characterize the heterogenic nature of these disorders, instead of trying to pinpoint which single cognitive construct or brain anomaly underlies all related characteristics. The question is whether there is indeed enough knowledge to select these potential intermediate cognitive phenotypes.

Objectives:   To give an overview of studies showing the cognitive overlap and differences between ADHD and autism and discuss whether cognitive profiles might be potential intermediate phenotypes.

Methods:   Two examples of one cognitive domain, i.e., cognitive control, will be given to illustrate the type of studies that are executed to study ADHD and autism in tandem. Children with ADHD will be directly compared with children on interference control and response variability.  

Results:   There are various cognitive domains were both disorders overlap in their cognitive deficits, however in some domains ASD and ADHD are clearly distinct. The two studies show that by detailed analyses differences between the two disorders can be detected while on first sight there seems to be a large overlap.

Conclusions: More detailed comparisons on cognitive domains between ADHD and autism are needed to determine which cognitive domains are potential intermediate phenotypes that help us in understanding the overlap. However, while inhibitory control might indeed be a potential intermediate phenotype, this seems not to be the case for intra-individual variability.