The Many Faces of Autism: Implications for assessment and association with anxiety

Autism Spectrum Disorder (ASD) is a complex and heterogeneous disorder, making it difficult to accurately identify ASD, especially in certain groups such as girls.
The first aim of this thesis was to contribute to the identification of ASD by examining the role of screening instruments, informants, and changes in diagnostic criteria, and differences between boys and girls in the identification and diagnosis of an Autism Spectrum Disorder.
The heterogeneity of ASD does not only consist of variations in the levels of core symptoms but also includes variations in associated psychopathology. One of the most frequently reported cooccurring psychiatric problems in children with ASD are anxiety problems. Therefore, the second aim of this thesis was to increase our understanding of the frequent co-occurrence of ASD and anxiety by investigating interrelationships between ASD and anxiety, both in families and in children with ASD over time.
These research questions were investigated in the Social Spectrum Study, a multicenter cohort of clinically referred children, who were all screened for the presence of ASD characteristics, of which a subsample received in-depth diagnostic assessment to establish to presence of ASD.