Anxiety in young people with intellectual disability

Investigators:

Mr Russell Nunn
Professor Bruce Tonge

Research to date:

Whilst there have been numerous studies investigating the prevalence and treatment of anxiety and phobic disorders in children and adolescents of normal intellectual ability, there remains a paucity of research for those with an intellectual disability (ID). This may be due to a false belief that people with an ID are protected from the development of mental illness, such as anxiety disorders.

The ACAD study has confirmed that psychopathology in young people with ID is a serious public health problem in our community, with many experiencing severe anxiety problems. Results also show that anxiety problems often emerge early in life in children with ID and remains relatively stable over time. It is clear that "internalising" problems are prevalent among young people with ID. Moreover, these emotional problems cause much distress and interfere with the development of adaptive functioning skills necessary for successful integration within the community, school and home settings.

The aims of anxiety study are:

• Develop and validate a scale for assessing anxiety in children with intellectual and developmental disabilities
• Examine a range of potential biopsychosocial predictors of anxiety in children with ID and various syndromes associated with ID, e.g. Down syndrome, Fragile X syndrome, autism etc.
• Using structural equation modelling, develop and test an explanatory model of anxiety in young people with intellectual disability
• Using multilevel modelling, assess developmental trajectories of anxiety over time
  

Preliminary Results:

A Brief Rating Scale for Assessing Anxiety in Children with Intellectual Disability

A subset of items from the Anxiety subscale of the DBC effectively discriminates between persons with and without an anxiety disorder. To avoid confusion with the DBC Anxiety subscale, this scale is termed the Anxious Behaviour Rating Scale (ABRS). The items in the ABRS are:

Item 16: Distressed about being alone
Item 22: Excessively distressed if separated from familiar person
Item 23: Fears particular things or situations
Item 30: Has nightmares, night terrors or walks in sleep
Item 75: Shy
Item 85: Tense, anxious, worried
Item 91: Upset and distressed over small changes in routine or environment

One-factor confirmatory factor analysis in LISREL of the ABRS items produces a model with good fit (Chi-squared=19.60, d.f.=13, p=.106; RMSEA=.031, GFI=.995) and maximised scale reliability (rm=.797).

A construct validation study has shown that the ABRS correlates significantly with two established measures of childhood anxiety: the Fear Survey Schedule for Children - Revised (r=.63) and the Trait Scale of the State-Trait Anxiety Inventory for Children (r=.73). In addition, persons with a DSM-IV diagnosed anxiety disorder score significantly higher on the ABRS compared to those without an anxiety disorder.

Developmental Trajectories of Anxiety in Young People with Intellectual Disability

In the area of developmental psychopathology, longitudinal studies play a vitally important role. Unfortunately, many researchers continue to analyze their data using traditional techniques based on the general linear model that fail to adequately account for the measurement, distributional or structural properties of their data. Over recent years, a new class of techniques for analyzing change has emerged which overcome many of these problems. Variously known as hierarchical linear models, random coefficient regression and multilevel models, these analytic approaches include the ability to handle missing observations and unequal spacing of measurement occasions. They are also well suited to handling time-varying and time invariant predictors. Furthermore, the ability of these techniques to assess trends at an individual level is particularly useful in psychopathology research where substantial between-subjects variations are common. In this study, multilevel modelling was used to assess trajectories of anxiety development in a longitudinal study of 570 young people with intellectual disability and separate samples of children with Down syndrome, Fragile X syndrome, Williams syndrome and autism. The analyses revealed substantial variations in anxiety problems across individuals and significant differences across syndrome groups.


Further information:

Russell Nunn (03) 9594 1300