The Broader Autism Phenotype in the Parents of Children With Autism Spectrum Conditions

Sucksmith, Edward (2012). The Broader Autism Phenotype in the Parents of Children With Autism Spectrum Conditions. PhD thesis The Open University.



Progress in our understanding of the aetiology of Autism Spectrum Conditions (ASC) can be informed by research into the expression of the Broader Autism Phenotype (BAP) in the unaffected genetic relatives of people with ASC. This thesis commences with a comprehensive literature review of the BAP (chapter one), followed by an online study into the BAP in people with ASC, their first-degree relatives and controls focusing on empathy and basic facial emotion recognition (chapter two). Results provide support for the BAP in male first-degree relatives (fathers) who self-reported significantly lower empathy than controls. After setting out the general methods (chapter three), three further empirical studies are described (chapters four to six) that assess whether there are quantitative differences in the expression of autistic traits and related phenotypes in the unaffected parents of simplex (single incidence) and multiplex (multiple incidence) autism families. Multiplex parents were significantly less accurate than simplex parents at attributing mental states to others after controlling for verbal intelligence and performed significantly worse than either simplex parents or controls at identifying specific negative basic emotions from facial expressions. These significant differences in the social domain provide support for the hypothesis that differential genetic mechanisms operate in multiplex and simplex autism. There was also significantly greater aggregation of ADHD traits in multiplex families compared to simplex families, which supports the hypothesis of genetic overlap between ASC and ADHD and bolsters future investigations of crosssyndrome endopheno types for these conditions. The final empirical study of this thesis (chapter seven) explores the hypothesis that autistic characteristics are ‘fractionable’ in ASC parents in ways that are consistent with the DSM-5 defined dyad of behavioural impairments characterizing clinical ASC. The thesis concludes with a summary of findings and implications for future autism research and clinical practice, together with suggestions for future directions in the area of BAP research (chapter eight).

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