Neuropsychological Functioning in Young Children with Williams Syndrome: A Longitudinal Study

Williams syndrome (WS) is a relatively rare neurodevelopmental disorder caused by a sporadic microdeletion on chromosome 7q11.23 (Fryssira et al., 1997; Korenberg et al., 2000). As a multisystemic disorder, WS has a distinctive profile of cognitive, physical, behavioural, and psychological characteristics. While there has been a considerable amount of research into the various aspects of intellectual and cognitive functioning in WS individuals, previous studies have tended to utilise samples that cover a wide age range (most commonly school-aged children and adults) and, as such, there is very little research focused on young WS children. Moreover, not much is known about the early developmental trajectories and/or early manifestations of the WS neuropsychological phenotype. Across four papers, this dissertation aims to identify the specific early cognitive predictors that contribute to later executive, social, psychological, and academic outcomes of young children with WS.

The General Introduction of this dissertation provides a broad overview of the WS literature relating to executive functioning, anxiety, sociability, and academic performance. There are four empirical chapters following this general introduction, each presenting a longitudinal design over approximately a 3.5-year period. Chapter 1 (Paper 1) investigated everyday executive functioning and its development over time in preschool children with WS. Individual variability was also examined. Chapter 2 (Paper 2) examined the prevalence and developmental course of the different types of anxiety symptoms found in very young children with WS, and how environmental, significant life events, demographic characteristics, and IQ impact anxiety over time. Chapter 3 (Paper 3) aimed to identify the early social profile and the early predictors that underpin later social functioning in young WS children. Chapter 4 (Paper 4) examined the early emerging profile of reading and mathematical abilities and identified early cognitive predictors of later academic functioning in young children with WS in comparison to TD controls. Individual variability was also examined in each empirical chapter. The General Discussion concludes the dissertation by discussing and interpreting the principal findings of the dissertation, which are as follows: i) The profiles of executive functioning, anxiety, social functioning, and academic achievement in this young WS cohort vastly parallels the profiles seen in older children and adults with WS; ii) Young WS children display considerable individual variability across the various neuropsychological abilities examined; iii) The gap in ability level between WS children and their neurotypical peers is widening with chronological age.

The areas of interest for future research that lead directly from the findings of this dissertation include: collaborative treatment studies examining behavioural, academic, psychological, and pharmacological therapies; further longitudinal studies to clarify the developmental precursors of later neuropsychological functioning in WS, and, finally, large, trans-disciplinary, and international research studies are required in order to progress this field further.