Intellectual disabilities (ID) or ‘learning disabilities’ affect approximately 1.5 million people in the UK. Nearly a quarter of these individuals are under the age of 18. Individuals with ID have been known to have higher levels of emotional issues and close to 40% of children and adolescents with ID in the UK may have other mental health issues, including anxiety.Mental health disorders such as anxiety are common amongst the UK population with an estimated 1 in 6 people experiencing a neurotic disorder such as anxiety or depression each year.
Anxiety disorders are also estimated to affect 3.3% of children and young adults in the UK. It is unclear, however, how common anxiety disorders are amongst children and adolescents with ID.
Examining mental health disorders in those with ID has proved challenging as mental health symptoms may be attributed to the ID – known as ‘diagnostic overshadowing’.
This has resulted in a gap in our understanding of the mental health issues faced by those with ID, particularly in young people. A recent study conducted by researchers from Monash University, Australia aimed to address this gap by examining the prevalence and assessment of anxiety disorders in children and adolescents with ID.
A systematic review of relevant literature was undertaken in April, 2014. A systematic review is used to appraise and summarise the results and implications of a breadth of research in a specific area and this approach to examining the prevalence and measurement of anxiety in children and adolescents with ID seemed well fitting given that there is little research on the area.
Two electronic databases (OVID Medline, PsycInfo) and leading disability journals (e.g. Journal of Intellectual Disability Research) were searched using a range of key terms to find articles relating to i) prevalence and ii) measurement/assessment of anxiety disorders in those with ID.
Studies on prevalence were restricted to those in English that were based on DSM/ICD diagnostics, had a minimum of 50 participants, ≥70% of which had ID.
Studies that considered anxiety measurement in those with ID were included if they were in English, presented reliability and validity statistics and ensured ≥70% of sample participants had ID.
Seven studies were found and the prevalence of anxiety disorders in these studies showed rates of anxiety disorders ranged from 3% to 22%. The highest rates of separation anxiety disorder were found in studies with five year olds. The highest rate of social anxiety disorder was found in 9 year olds (10.8%).
Generalised anxiety disorder prevalence was lower than the former two disorders, and ranged from 0% to 5.4% in two studies that examined this.
Specific phobias were considered in three studies. One study showed that 17.5% of study participants had a specific phobia, but in the other two studies prevalence was only 2%.
Twenty-one studies that examined the psychometric measurement of anxiety disorders were found that met inclusion criteria. Across these 21 studies, there were 13 instruments used for anxiety used in children and/or adolescents that met this study’s inclusion criteria.
Some of these could be completing through self-reporting or through someone else (usually a parent) providing responses to questions in the instrument. One was to be completed with clinicians. Instruments included, for example, the Child Behaviour Checklist (CBCL), containing a section that measures anxiety/depression and the Baby and Infant Screen for Children with aUtism Traits (BISCUIT – Part 2) which has a subscale for anxiety and repetitive behaviour.
Some of the instruments cited were modified for use with typically developing children/adolescents (e.g. Revised Children’s Manifest Anxiety Scale; RCMAS).
Three instruments were developed specifically for children and adolescents with ID: Reiss Scales for Children’s Dual Diagnosis (RSCDD), the Nisonger Child Behaviour Rating Form (NCBRF) and the Developmental Behaviour Checklist (DBC). These scales provide a broad assessment of behaviour and emotional problems in children/adolescents with ID with a subscale to measure anxiety included. The NCBRF and DBC showed the best reliability and validity.
Some reviews found by the authors, but not included in the systematic review, examined the psychometric properties of anxiety measures used in samples of children/adolescents with autism specifically, demonstrating that research into autistic populations was further ahead than ID populations.
The authors concluded that:
Several existing measures hold potential as reliable and valid measures of anxiety symptoms in children and adolescents with intellectual disability … However, further evaluation studies in the target population are required to firmly establish the psychometric properties of these measures of anxiety. In addition, the capacity of the measures to screen for anxiety disorders in young people with ID remains to be established.
Whilst these conclusions seemed reasonable given the data retrieved from the systematic review, different conclusions may have been reached if the authors considered a wider range of literature. The need for further research into examining anxiety disorders in children and adolescents is a fair point as research in this area is lagging behind, for example, equivalent research into autism.
Strengths and limitations
The strengths of the study were that it was that it was the first research of its kind examining prevalence and measurement of anxiety disorders in children and adolescents with ID. The researchers also scrutinised the papers extract figures on prevalence, reliability and validity thoroughly and presented relevant statistics.
There were, however, a number of weaknesses. For example, the researchers only used two main electronic databases and several individual journal searches. This limited the breadth of literature they could have found on the topic. Additionally, whilst the authors only considered studies where the majority of participants were ≤17, this was not justified.
There have been calls for the classification of adolescents to be raised to 25, (Wallis, 2015) therefore, the rationale for what constitutes adolescents was needed.
Finally, studies’ participants differed in terms of degree of ID, therefore, conclusions drawn about prevalence of anxiety disorders in children/adolescents with ID is not wholly accurate.
The prevalence of anxiety disorders in children and adolescents with ID is higher than that in the typically developing population of children and adolescents. Given that there are higher rates of anxiety and other mental health problems (e.g. depression) in this population, it is important to think deeply about how best to support these individuals.
They are more likely to face emotional setbacks and may require more emotional support or therapeutic interventions where appropriate.
Whilst the development of assessments of anxiety in children and adolescents with ID is still clearly in its infancy, there is some promise in a few instruments (e.g. RSCDD; NCBRF; DBC) to measure the level of anxiety in these individuals.
Whilst these instruments have not yet demonstrated their ability to successfully screen children and adolescents with ID for anxiety symptoms, future work in the area should lend itself towards the ability to do so.
Young people with autism have been researched more than those with ID, whilst ID may be more common, and more research into those with ID is needed to develop our understanding of how we can support children and adolescents with ID to the best of our ability.
Anxiety disorders in children and adolescents with intellectual disability: Prevalence and assessment, Reardon T, Gray K, Melvin G, in Research in Developmental Disabilities, 36, 175–190 [Abstract]
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