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Executive functioning in autism spectrum disorders: influence of task and sample characteristics and relation to symptom severity

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Abstract

Impaired executive functioning (EF) has been proposed to underlie symptoms of autism spectrum disorders (ASD). However, insight in the EF profile of ASD individuals is hampered due to task impurity and inconsistent findings. To elucidate these inconsistencies, we investigated the influence of task and sample characteristics on EF in ASD, with an extended test battery designed to reduce task impurity. Additionally, we studied the relation between EF and ASD symptoms. EF (inhibition, cognitive flexibility, generativity, working memory and planning) was measured in open-ended versus structured assessment situations, while controlling for possible confounding EF and non-EF variables. The performance of 50 individuals with ASD was compared with that of 50 age, gender and IQ matched typically developing (TD) individuals. The effects of group (ASD versus TD), age (children versus adolescents) and gender were examined, as well as the correlation between age, IQ, ASD symptoms and EF. Individuals with ASD showed impairments in all EF domains, but deficits were more pronounced in open-ended compared to structured settings. Group differences did not depend on gender and only occasionally on participants’ age. This suggests that inconsistencies between studies largely result from differences in task characteristics and less from differences in the investigated sample features. However, age and IQ strongly correlated with EF, indicating that group differences in these factors should be controlled for when studying EF. Finally, EF correlated with both social and non-social ASD symptoms, but further research is needed to clarify the nature of this relationship.

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Notes

  1. Miyake and Friedman [8] suggested that inhibition is a common component in all EF tasks. Therefore, if one EF measure correlated with an inhibition variable (and group differences were found on both measures), we included the inhibition variable as a covariate in the group analyses of that EF measure, but not vice versa.

  2. Since ADHD is the psychiatric disorder that most often co-occurs with ASD and is the co-occurring disorder that is most linked with EF, we focused on the possible influence of this disorder. The ASD sample excluding individuals with a co-occurring ADHD diagnosis was still matched with the TD sample for age (p = 0.96), PIQ (p = 0.76), TIQ (p = 0.16) and gender-ratio (p = 0.62), but not for VIQ (p = 0.02), as was the case for the full ASD sample (n = 50).

  3. No correlations were found with laboratory main EF variables (that measure a different EF domain), suggesting that there are no confounding EF measures that should be controlled for (see Table 2 in Online Resource 1).

  4. Although we did demonstrate that significant group differences on the main EF measures remained after excluding the individuals with ASD and co-occurring ADHD.

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Acknowledgments

L. Van Eylen is a doctoral and B. Boets a post-doctoral research fellow of the Research Foundation Flanders (FWO). Additionally, the research was funded by a fellowship from the Marguerite-Marie Delacroix to L. Van Eylen and a grant from the Research Council of KU Leuven (IDO/08/013). We thank all participants, and all master students as well as B. Machilsen, A. Verhappen and V. Stevens for assistance in data collection and scoring.

Conflict of interest

On behalf of all authors, the corresponding author states that there is no conflict of interest.

Ethical Standards

The study protocol was approved by the Medical Ethical Committee of the University Hospitals Leuven and the Ethical Committee of the Faculty of Psychology and Educational Sciences of the KU Leuven and was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.

Informed consent

Informed consent was obtained from the participants’ parents and from participants aged 16 years or older. The study protocol was approved by the Medical Ethical Committee of the University Hospitals Leuven and the Ethical Committee of the Faculty of Psychology and Educational Sciences of the KU Leuven.

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Authors and Affiliations

  1. Parenting and Special Education Research Unit, KU Leuven, Leopold Vanderkelenstraat 32, Box 3765, 3000, Leuven, Belgium

    Lien Van Eylen & Ilse Noens

  2. Leuven Autism Research (LAuRes), KU Leuven, Leuven, Belgium

    Lien Van Eylen, Bart Boets, Jean Steyaert, Johan Wagemans & Ilse Noens

  3. Department of Child Psychiatry, UPC-KU Leuven, Leuven, Belgium

    Bart Boets & Jean Steyaert

  4. Laboratory of Experimental Psychology, KU Leuven, Leuven, Belgium

    Johan Wagemans

  5. Department of Clinical Genetics, University Hospital Maastricht, Maastricht, The Netherlands

    Jean Steyaert

  6. Psychiatric and Neurodevelopmental Genetics Unit, Massachusetts General Hospital, Boston, USA

    Ilse Noens

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  1. Lien Van Eylen
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Correspondence to Lien Van Eylen.

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Van Eylen, L., Boets, B., Steyaert, J. et al. Executive functioning in autism spectrum disorders: influence of task and sample characteristics and relation to symptom severity. Eur Child Adolesc Psychiatry 24, 1399–1417 (2015). https://doi.org/10.1007/s00787-015-0689-1

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