| Summary: | Repetitive and restricted behaviours have been considered as a core symptom of autism since the first descriptions provided by Leo Kanner (Kanner, 1943) and Hans Asperger (Asperger, 1944), and this view has been supported through all the incarnations of international diagnostic systems. However, when compared with other core features: problems in communication and problems in reciprocal social interaction, repetitive behaviours have been relatively neglected in terms of research. In particular, little is known about the triggers for repetitive behaviours and what functions they might serve for individuals with autism. Early theoretical accounts of autism proposed that sensory problems and anxiety are the key triggers for repetitive behaviours. Research in the field of developmental psychology has also demonstrated that in very young children, repetitive behaviours serve the function of constraining sensory unpredictability and warding of anxiety and this relationship has also been found in individuals with Obsessive Compulsive Disorder, a condition defined by anxiety and ritualism. However, the three way relationship between repetitive behaviours, sensory problems and anxiety has not been explored in the autism literature before. The main aim of the thesis (Part 1) was to explore this relationship in children with autism. In addition to this main focus, the work of the thesis also included a study of the mothers of the same children (Part 2), investigating mothers‘ own anxiety, sensory correlates of this anxiety and other factors. The main effects of autism are on the individual who is on the autism spectrum, however, impact is also felt by families. Parents of children with autism have been found to have higher prevalence of affective disorders when compared to both parents of typically developing children and parents of children with other disabilities. The second main aim of the thesis was to explore correlates of anxiety in mothers of children with autism. In Part 1, a series of studies are reported using questionnaire data to investigate repetitive behaviours (RRBs), anxiety and sensory problems in children with autism. Part 2, focused on anxiety in the mothers of these children and correlates of their anxiety. The first empirical chapter (Chapter 3) examined RRBs in children with and without autism and validated the Repetitive Behaviour Questionnaire-2 (RBQ-2; Leekam et al., 2007) for the first time with children with autism. Results indicated that the RBQ-2 provides a highly reliable measure of repetitive behaviours for children with autism aged from 2 to 17 years. Factor analysis revealed that a two-factor structure with the repetitive motor and sensory behaviour (RSM) factor and the insistence on sameness (IS) factor best represented the data. Internal consistency was high for both the total RBQ-2 scale and for each RSM and IS subscale separately. This chapter also explored moderators of repetitive behaviours in children and adolescents with autism and found that while RSM behaviours were negatively associated with lower chronological age, and lower expressive language levels, IS behaviours were not. Further analysis was conducted using a secondary dataset from a longitudinal study of RRBs in typically developing children at age 15, 24 and 72 months old. Results showed that IS and RSM behaviours represent relatively independent classes of behaviours in developmental terms. The second empirical chapter (Chapter 4) examined anxiety in children with autism and provided validation for the school age and preschool version of the Spence Anxiety Scales. Using this scale it was found that as many as 49% of children with autism met the criteria for elevated overall anxiety and that separation anxiety and physical injury fears were the most prevalent anxiety subtypes. Good agreement on total anxiety scores between children‘s and parents‘ reports was found. Analysis on the mediators of anxiety suggested that anxiety was not associated with chronological age, impairments in communication and social interaction, and expressive language levels. The third empirical chapter (Chapter 5) provided evidence that sensory problems in children and adolescents with autism are both multisensory and multimodal in nature. More precisely, only 2 children had problems in a single sensory modality while on the other hand, 40% of children had problems simultaneously across all five primary sensory modalities. Almost 91% of children and adolescents showed mixed types of sensory modulation problems, with 65.3% of children having problems in all four sensory quadrants (sensory hyper- and hypo-sensitivity, seeking, and avoidance). This chapter also explored the mutual relationship between the four sensory subscale (quadrants) of the Sensory Profile. Results indicated that children and adolescents with autism fluctuate between the states of hypo- and hyper-responsiveness; that avoidance behaviours are compensatory strategies related to being over-stimulated, and that seeking behaviours are more related to being over-stimulated rather than hypo-stimulated. The final chapter in Part 1, Chapter 6, examined the interrelations between RRB, sensory problems and anxiety. Results showed that both insistence on sameness (IS) and repetitive motor (RM) behaviours were associated with sensory problems. However, only IS behaviours were associated with anxiety while RM behaviours were not. Meditation analyses models showed that sensory sensitivity and anxiety were reinforcing each other in the relationship with IS behaviours. The two chapters in Part 2 examined the frequency and correlates of anxiety in mothers of children with autism. Findings from these two chapters (Chapters 8 and 9) suggested that anxiety is very prevalent among mothers of children with autism with 46% of mothers meeting the cut-off criteria for clinically significant anxiety. For the first time, sensory problems in mothers were examined, and were also found to be very prevalent in mothers, appearing in 60% per cent of mothers. The frequency of sensory features in mothers was correlated with the frequency of sensory features in their children. Further analysis suggested that higher levels of sensory over-sensitivity, higher levels of intolerance of uncertainty, and the dominant use of escape-avoidance coping style contributed to anxiety levels in mothers. Furthermore, it was found that sensory sensitivity in mothers was related to their higher use of escape-avoidant coping strategy and the mediation analysis suggested that sensory sensitivity, escape-avoidance coping and anxiety reinforced each other. The importance of these findings for future theoretical and clinical work is considered in detail in the general discussion chapter (Chapter 10).
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