Executive functioning in individuals with intellectual disabilities and autism spectrum disorders.
BACKGROUND
Executive functioning (EF) is important for adequate behavioural functioning and crucial for explaining symptoms of autism spectrum disorders (ASD) in individuals with normal intelligence, but is scarcely studied in individuals with ASD and intellectual disabilities (ID). We therefore study EF in an ID population by comparing performances on three frequently studied executive functions (shifting, inhibition and updating) between individuals with ASD and individuals without ASD. When studying ID populations, one should be aware of Spearman's Law of Diminishing Returns (SLODR), as it questions the possibility of measuring separate cognitive functions in ID populations.


METHODS
Six EF tasks were administered to 50 individuals with mild to borderline ID, of which half was diagnosed with ASD. In order to investigate the distinctness of the three executive functions in this ID sample, the results on the six EF tasks were subjected to principal components analysis (PCA). Subsequently, a multivariate analysis of variance (MANOVA) was performed to assess differences between the ASD and non-ASD group on shifting, inhibition and updating.


RESULTS
The PCA revealed the hypothesised EF trichotomy. MANOVA analysis showed no significant group differences on EF-performance.


CONCLUSIONS
Three separate executive functions were measured in this ID population, but despite much evidence that individuals with ASD display more behavioural problems and the proven relevance of EF in behavioural functioning, no significant group difference was found on shifting, inhibition or updating. After this first effort to achieve more insight into EF of individuals with ASD and ID the relation between behavioural problems and EF will require further study.
Department of Medical Psychology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; Centre of Excellence for Neuropsychiatry, Vincent van Gogh Institute for Psychiatry, Venray, The Netherlands.
R L
RL
Roelofs
E M
EM
Visser
H J C
HJ
Berger
J B
JB
Prins
H M J
HM
Van Schrojenstein Lantman-De Valk
J P
JP
Teunisse
D000328:Adult; D000704:Analysis of Variance; D002659:Child Development Disorders, Pervasive / Q000523:psychology*; D056344:Executive Function / Q000502:physiology*; D005260:Female; D006801:Humans; D008607:Intellectual Disability / Q000523:psychology*; D008297:Male; D009426:Netherlands; D009483:Neuropsychological Tests; D025341:Principal Component Analysis; D055815:Young Adult
autism spectrum disorders (ASD); executive functions (EF); intellectual disabilities (ID)