Sleep is essential to our overall functioning and wellbeing. Children on the autism spectrum experience high rates of sleep problems that can be both chronic and severe, and which are associated with a wide range of detrimental effects for children and their families. Sleep problems can intensify the core symptoms of autism, including restricted and repetitive behaviours commonly known as stereotypy. The aetiology of sleep disturbance in autism is multifactorial, involving biological, psychological, social, medical, and environmental factors. Notwithstanding these determinants, sleep problems often have a behavioural basis. Functional behaviour assessment (FBA) is an evidence-based approach to identifying the environmental and behavioural factors underlying sleep problems for an individual, and to guiding the selection of behavioural sleep interventions (BSI).

Children on the autism spectrum may engage in stereotypy at night, which may contribute to sleep problems by delaying sleep onset or the re-initiation of sleep following night wakings (NWs). It is generally unclear, however, whether established BSI techniques can effectively treat sleep-related stereotypy, particularly when it is automatically maintained, or which types of strategies may be required to treat such behaviour. Further, little is known about the characteristics of sleep-related stereotypic behaviours, nor its role in relation to sleep, including the extent to which stereotypy contributes to or is a co-occurring feature of sleep disturbance. Finally, there is lack of research investigating whether improving sleep problems may result in collateral benefits for children and parents, including children’s daytime stereotypy and wider symptoms of autism.

The primary objectives of the present research were three-fold: (1) to investigate the effectiveness of function-based BSI to treat stereotypy in the context of sleep problems in children on the autism spectrum, and to examine the maintenance of treatment effects and acceptability to parents of the selected treatments; (2) to investigate whether and how stereotypy may contribute to sleep disturbance, and the characteristics (e.g., type, topography, function) of sleep-related stereotypy across individuals; and (3) to examine whether treating sleep problems produces collateral benefits for children and parents, including change in children’s daytime stereotypy. Three empirical studies in this thesis used single-case experimental (multiple baseline or AB) design to evaluate the utility of function-based BSI to treat sleep problems including sleep onset delay (SOD) and NWs in 12 children (5 girls and 7 boys, aged 3-10 years) with formal diagnoses of autism spectrum disorder. In 10/12 children, sleep-related stereotypy occurred during SOD and/or NWs and appeared to interfere with the initiation and/or re-initiation of sleep.

A fourth, qualitative study thematically analysed the clinical assessment reports for 15 children on the autism spectrum (aged 3-15 years; including the children in Studies 1-3) to further examine the potential role of stereotypy within sleep problems, and characteristics of children’s behaviour. A systematic review of the research literature was conducted to investigate the types of collateral effects that may occur following a BSI for children on the autism spectrum. Psychometric measures administered pre- and post-treatment in Studies 1-3 of this thesis were used to assess whether the BSI produced change in core symptoms of autism and internalising and externalising symptoms in participant children, as well as in parents’ sleep quality, wellbeing, and relationship quality, with data examined using modified Brinley plots.

Collectively, results demonstrate the preliminary effectiveness, durability, feasibility, and social validity of a variety of function-based BSI, including preliminary evidence for strategies that may effectively reduce automatically maintained sleep-related stereotypy.

Tentative support was found for procedures that manipulate the motivating operations for stereotypy and sleep, including sleep restriction. Findings demonstrate that a heterogeneous range of behaviours including motor and vocal stereotypy and repetitive manipulation of objects can accompany sleep problems in children on the autism spectrum and may contribute to sleep disturbance by delaying the initiation of sleep, and/or re-initiation of sleep following NWs.

Results also showed that stereotypy may differentially affect sleep across and within children, which may have differing implications for behavioural treatment. Finally, an evaluation of the collateral effects of BSI in the research literature and in participant children and parents in Studies 1-3 indicate that BSI may produce a range of untargeted, beneficial effects including a reduction in children’s daytime stereotypy, however, collateral effect results were mixed and inconsistent. Overall, findings emphasise the importance of utilising FBA to inform BSI for children on the autism spectrum, which may necessarily include strategies that specifically target automatically maintained behaviour. Future research is needed to better understand how sleep problems and core symptoms of autism interact across and within children, and address how these relationships are treated in the sleep context.