ADHD item profiles in children and adolescents with autism spectrum disorder

Background: Although attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorders (ASD) represent different nosological entities they share symptoms such as hyperactivity, impulsivity, and inattention. Psychopathological, genetic and neuropsychological findings indicate an association between both disorders.

Objectives: The aims of this systematic prospective study were to evaluate ADHD like symptoms in ASD children based on single item-analysis and their association with ASD diagnosis, age, gender and IQ as well as the comparison of a non-ADHD (ASD-) and an ADHD (ASD+) sample.

Methods: Participants were 83 children and adolescents with ASD. Dimensional and categorical aspects of ADHD were evaluated using a diagnostic symptom checklist and a parent ADHD symptom questionnaire according to DSM-IV. Furthermore PDD and ODD/CD symptoms were assessed.

Results: 53% of the sample fulfilled DSM-IV criteria for ADHD. The comparison of the ASD+ and the ASD- sample revealed differences in age and IQ. The severity of ADHD symptoms in the ASD+ sample was associated with the type of ASD diagnosis. Correlations of ADHD and PDD showed significant results for symptoms of hyperactivity with impairment in communication and for inattention with stereotyped behaviour. Item profiles of ADHD symptoms in the ASD+ sample were similar to those in a pure ADHD sample.

Conclusions: Results of our study revealed a high phenotypical overlap between ASD and ADHD. Two subtypes, one being “inattentive-stereotyped” and the other “hyperactive-communication impaired” can be identified. This fact reflects the DSM-classification for ADHD and may theoretically be a sign of two different neurochemical pathways, a dopmaninergic and a serotonergic.

A very detailed examination and exploration can help to understand within the presented child with ASD whether the reported ADHD like symptoms support the notion of an ADHD behavioural syndrome or an increased rate of single behaviours in order to provide the adequate treatment.