| Summary: | Autism Spectrum Disorder (ASD) is a heritable neurodevelopmental condition. In addition to the core symptoms, numerous physical and mental health issues commonly co-occur with ASD, notably anxiety disorders. Despite its high prevalence, the nature of anxiety within ASD remains poorly understood. This thesis investigated the prevalence, neurocognitive correlates and longitudinal predictors of co-occurring anxiety in children at familial high-risk for ASD (HR, n=42) and low-risk controls (LR, n=37) aged 6-8 years. The HR group was divided into those who met diagnostic criteria for ASD (HR-ASD, n=15) and those who did not (HR-non ASD, n=27). This thesis had three broad aims. Primarily, the prevalence of co-occurring anxiety and its association to the core symptoms of ASD was investigated in the HR and LR groups using both parent- and self-report. A further aim was to investigate whether the cognitive correlates of anxiety observed in non-ASD populations (such as increased attentional bias to threat) were also present in the HR-ASD and HR-non ASD groups. The final aim was to examine whether dysregulated temperament (high levels of Negative Affect and low Effortful Control) in infancy and toddlerhood predicted anxiety symptoms in middle childhood in the HR and LR groups. The HR-ASD group had high levels of parent-reported anxiety, which were associated with the core symptoms of ASD. However, they did not exhibit enhanced bias to threatening stimuli. On the other hand, the HR-non ASD group had somewhat elevated anxiety on specific subscales but did manifest heightened attentional bias to threat. Finally, Negative Affect at the age of 7 months was associated with anxiety at 6-8 years in all groups. Taken together, these findings suggest that anxiety is highly prevalent in children at high-risk for ASD, but that there may be differential neurocognitive correlates among high-risk children who develop ASD and those who do not.
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