Longitudinal trajectories of intellectual and adaptive functioning in adolescents and adults with Williams syndrome

• Published in: Journal of intellectual disability research 2016-10, Vol.60 (10), p.920-932
• Main Authors: Fisher, M. H., Lense, M. D., Dykens, E. M.
• Format: Article
• Language: English
• Subjects: Adaptation, Psychological - physiology; Adaptive behavior; adaptive functioning; Adjustment (to Environment); Adolescent; Adolescents; Adult; Adults; Age differences; Attention deficits; Behavior; Behavior Rating Scales; Childhood; Cognitive Ability; Cognitive aspects; Cognitive Development; Cognitive functioning; Cognitive-behavioral factors; Daily Living Skills; Developmental Stages; Disability; Evaluation; Female; Genetic Disorders; Humans; Individual differences; Intellectual ability; Intellectual disabilities; Intellectual Disability; Intellectual functioning; Intelligence; Intelligence - physiology; Intelligence Quotient; Intelligence Tests; Learning disabilities; Life course; Living skills; longitudinal; Longitudinal Studies; Male; Men; Middle Aged; Moderate Intellectual Disability; Neurological disorders; Scores; Socialization; Teenagers; Variability; Williams syndrome; Williams Syndrome - physiopathology; Young Adult
• ISSN: 0964-2633; 1365-2788
• DOI: 10.1111/jir.12303

Background Williams syndrome (WS) is associated with a distinct cognitive‐behavioural phenotype including mild to moderate intellectual disability, visual‐spatial deficits, hypersociability, inattention and anxiety. Researchers typically characterise samples of individuals with WS by their intellectual functioning and adaptive behaviour. Because of the low prevalence of the syndrome, researchers often include participants with WS across a broad age range throughout childhood and adulthood and assume participants demonstrate consistent cognitive development across ages. Indeed, IQ scores are generally stable for children and adolescents with WS, although there are significant individual differences. It is less clear whether this pattern of stable intellectual ability persists into adulthood. Furthermore, while adaptive behaviour is an important indicator of an individual's ability to apply their conceptual skills to everyday functioning, conflicting findings on the trajectories of adaptive behaviour in adolescents and adults with WS have been reported. The current study examined longitudinal profiles of cognitive and adaptive functioning in adolescents and adults with WS. Method To examine cognitive functioning, participants included 52 individuals with WS (51.9% men) who were assessed with the Kaufman Brief Intelligence Test, 2nd edition (KBIT‐2) between two and seven times. At their first assessment, participants had a mean age of 25.4 years (SD = 8.4), ranging in age from 14.2 to 48.9 years. To assess adaptive behaviour, participants included a subset of 28 individuals with WS whose parents completed the Vineland Adaptive Behavior Scale, 2nd edition (VABS‐II) between two and five times. At their initial administration, participants ranged from 17.1–40.2 years of age, with a mean age of 26.5 years (SD = 7.3). A series of multilevel models were used to examine changes in KBIT‐2 Composite IQ, Verbal IQ and Nonverbal IQ standard scores over time, as well as the Adaptive Behavior Composite, and the Communication, Daily Living Skills and Socialization subdomains of the VABS‐II. Results Consistent with the WS cognitive profile, IQ scores were significantly lower than the general population IQ score of 100, and there was significant variability in individual IQ scores and slopes. KBIT‐2 IQ scores were generally stable across adolescents and adults with WS. Adaptive behaviour scores were significantly lower than the population mean score of 100, and there was sig