Subgrouping siblings of people with autism: Identifying the broader autism phenotype.

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Ruzich, Emily 
Smith, Paula 
Auyeung, Bonnie 

We investigate the broader autism phenotype (BAP) in siblings of individuals with autism spectrum conditions (ASC). Autistic traits were measured in typical controls (n = 2,000), siblings (n = 496), and volunteers with ASC (n = 2,322) using the Autism-Spectrum Quotient (AQ), both self-report and parent-report versions. Using cluster analysis of AQ subscale scores, two sibling subgroups were identified for both males and females: a cluster of low-scorers and a cluster of high-scorers. Results show that while siblings as a group have intermediate levels of autistic traits compared to control individuals and participants with ASC, when examined on a cluster level, the low-scoring sibling group is more similar to typical controls while the high-scoring group is more similar to the ASC clinical group. Further investigation into the underlying genetic and epigenetic characteristics of these two subgroups will be informative in understanding autistic traits, both within the general population and in relation to those with a clinical diagnosis. Autism Res 2016, 9: 658-665. © 2015 The Authors Autism Research published by Wiley Periodicals, Inc. on behalf of International Society for Autism Research.

Autism-Spectrum Quotient, autism, autistic traits, broader autism phenotype, sex differences, siblings, Adolescent, Autistic Disorder, Child, Child, Preschool, Cluster Analysis, Female, Humans, Male, Parents, Phenotype, Self Report, Siblings
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Autism Res
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Medical Research Council (G0600977)
National Institute for Health Research (NIHR) (via Cambridgeshire and Peterborough NHS Foundation Trust (CPFT) (unknown)
This work was supported by grants from the Autism Research Trust, the MRC, and the Wellcome Trust to SBC. CA was supported by NIHR CLAHRC EoE during the period of this work.