Research in Developmental Disabilities 36 (2015) 175–190

Contents lists available at ScienceDirect

Research in Developmental Disabilities

Review article

Anxiety disorders in children and adolescents with intellectual disability: Prevalence and assessment Tessa C. Reardon, Kylie M. Gray *, Glenn A. Melvin Centre for Developmental Psychiatry and Psychology, Department of Psychiatry, School of Clinical Sciences, Monash University, Australia

A R T I C L E I N F O

A B S T R A C T

Article history: Received 27 September 2014 Accepted 2 October 2014 Available online

Children and adolescents with intellectual disability are known to experience mental health disorders, but anxiety disorders in this population have received relatively little attention. Firstly, this paper provides a review of published studies reporting prevalence rates of anxiety disorders in children and adolescents with intellectual disability. Secondly, the paper reviews measures of anxiety that have been evaluated in children/ adolescents with intellectual disability, and details the associated psychometric properties. Seven studies reporting prevalence rates of anxiety disorders in this population were identified, with reported rates varying from 3% to 22%. Two-one studies evaluating a measure of anxiety in a sample of children/adolescents with intellectual disability were identified. While these studies indicate that several measures show promise, further evaluation studies are needed; particularly those that evaluate the capacity of measures to screen for anxiety disorders, not only measure symptoms. ß 2014 Elsevier Ltd. All rights reserved.

Keywords: Anxiety disorders Intellectual disability Assessment Prevalence Children Adolescents

Contents 1. 2. 3.

4.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1. Overview of literature review . . . . . . . . . . . . . 3.2. Prevalence studies . . . . . . . . . . . . . . . . . . . . . . 3.3. Anxiety measures . . . . . . . . . . . . . . . . . . . . . . . 3.4. Evaluation studies . . . . . . . . . . . . . . . . . . . . . . 3.4.1. Evaluation of broad-based measures 3.4.2. Evaluation of anxiety measures . . . . Discussion and conclusions . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

176 176 177 177 178 178 182 182 186 187 188

* Corresponding author at: Centre for Developmental Psychiatry and Psychology, Early in Life Mental Health Service, Monash Medical Centre, 246 Clayton Road, Clayton, VIC 3168, Australia. Tel.: +61 03 9902 4563. E-mail address: [email protected] (K.M. Gray). http://dx.doi.org/10.1016/j.ridd.2014.10.007 0891-4222/ß 2014 Elsevier Ltd. All rights reserved.

176

T.C. Reardon et al. / Research in Developmental Disabilities 36 (2015) 175–190

1. Introduction The mental health of individuals with intellectual disability (ID) has received growing attention over recent years. Little more than forty years ago, it was widely presumed that individuals with ID could not experience mental health problems (Matson, Belva, Hattier, & Matson, 2012), however the elevated rates of mental health problems among individuals with ID is now well established (Dekker, Koot, van der Ende, & Verhulst, 2002; Einfeld & Tonge, 1996; Totsika, Hastings, Emerson, Lancaster, & Berridge, 2011). Although reported prevalence rates vary, population studies of children and adolescents with ID have repeatedly identified rates of comorbid mental health problems at 30–40% (Einfeld & Tonge, 1996; Linna et al., 1999; Rutter, Tizard, & Whitmore, 1970; Totsika et al., 2011). Relatively fewer studies have incorporated full psychiatric assessments (thus enabling diagnoses of mental health disorders), however, it is noteworthy that three studies that did, conducted in the UK, the Netherlands and Norway, report strikingly similar rates (36–39%) of DSM/ICD mental health disorders among children and adolescents with ID (Dekker & Koot, 2003; Emerson & Hatton, 2007; Stromme & Diseth, 2000). These figures are markedly higher than corresponding estimates of 8–17% in typically developing populations of young people (Costello, Mustillo, Erkanli, Keeler, & Angold, 2003; Emerson & Hatton, 2007; Merikangas et al., 2010; Roberts, Roberts, & Xing, 2007). With a larger literature base surrounding the mental health of typically developing children and adolescents, prevalence rates of specific mental health disorders are now better established, and anxiety disorders consistently emerge near the top of the list (Costello et al., 2003; Emerson & Hatton, 2007; Roberts et al., 2007). In contrast, efforts to establish corresponding prevalence rates of specific disorders, including anxiety disorders, among young people with ID is still in its infancy. The first aim of this paper is to review this emerging literature, and detail current best estimates of the prevalence of anxiety disorders among children and adolescents with ID. Recognition that mental health disorders not only exist, but also are highly prevalent among young people with ID has prompted interest in the development and evaluation of measures designed to identify these disorders in this population. Unique challenges associated with identifying a mental illness within the context of an intellectual disability have been identified, including, ‘diagnostic overshadowing’ – falsely attributing symptoms of mental illness to the intellectual disability (Reiss, Levitan, & Szyszko, 1982) – and the atypical and varying presentation of mental illness in this population (Bailey & Andrews, 2003; Cooper, Melville, & Einfeld, 2003). Such barriers to accurate diagnosis of mental health disorders among individuals with ID have highlighted the need for a targeted approach to mental health assessment in this population. A number of comprehensive broad-based questionnaires designed to identify mental health problems in young people with ID exist (e.g. the Developmental Behaviour Checklist, Einfeld & Tonge, 2002; Nisonger Child Behaviour Rating Form, Aman, Tasse´, Rojahn, & Hammer, 1996); and others designed for typically developing populations have been evaluated in young people with ID (e.g. the Child Behaviour Checklist, Achenbach, 1991a). However, the development and evaluation of measures to detect specific mental health disorders, including anxiety disorders, has received less attention. Recent reviews have provided comprehensive evaluations of existing measures for identifying anxiety (Hermans, van der Pas, & Evenhuis, 2011) and depression (Hermans & Evenhuis, 2010) in adults with ID; however studies evaluating measures in younger populations with ID are lacking. This paper aims to provide a corresponding review of existing anxiety measures evaluated in samples of children and adolescents with ID. Measures of anxiety that have been evaluated in children and/or adolescents with ID were identified and findings relating to the associated psychometric properties detailed. 2. Method A systematic review of the literature was conducted in order to (i) identify studies that have reported prevalence rates of anxiety disorders among children and/or adolescents with ID; (ii) identify measures (questionnaires, checklists or interviews) designed to detect anxiety that have been evaluated in a sample of children and/or adolescents with ID; and (iii) document reported reliability (internal consistency, test–retest, inter-rater) and validity (convergent/divergent, criterion, predictive) associated with each measure in children and/or adolescents with ID. The literature review was conducted in April 2014, and included three stages. Firstly, electronic databases (OVID Medline, PsychInfo) were searched using the search terms detailed in Table 1. Search terms in the four groups were combined with ‘AND’ and abstracts published in journal articles since 1980 were searched. Next, references lists in selected papers and citations of selected papers/measures were reviewed. Finally, the contents page (titles/abstracts) of leading disability journals published since 2009 were reviewed (Journal of Intellectual Disability Research; Research in Developmental Disabilities; Journal of Applied Research in Intellectual Disabilities; American Journal on Intellectual and Developmental Disabilities; Intellectual and Developmental Disabilities; International Journal of Developmental Disabilities; Journal of Intellectual and Developmental Disability; Journal of Autism and Developmental Disorders; British Journal of Learning Disabilities). In selecting anxiety prevalence studies for inclusion, the following criteria were applied: (i) study reported prevalence rate of any anxiety disorder based on a psychiatric interview and the application of DSM/ICD diagnostic criteria; (ii) at least 70% of the sample were aged 17 or less with an intellectual disability (or developmental delay); (iii) a representative sample of children and/or adolescents with intellectual disability (or developmental delay) was used, with a minimum of n = 50; (iv) paper was available in English. Prevalence studies were excluded if: (i) reported prevalence rates were measured using only screening measures or medical records; (ii) only rates of OCD or PTSD were reported; (iii) the sample only included individuals with autism spectrum disorder or individuals with intellectual disability from one specific etiological group

T.C. Reardon et al. / Research in Developmental Disabilities 36 (2015) 175–190

177

Table 1 Literature review: Terms used in search of electronic databases. Search terms Group Group Group Group

1 2 3 4

intellectual disabilit$ OR mental retard$ OR learning disabilit$ OR developmental delay OR developmental disabilit$ anxiety OR fear OR panic OR anxious OR psychopathology OR behavio$ OR emotion$ OR mental health OR psychiatric child$ OR youth OR young OR teen$ OR adolescen$ OR toddler prevalence OR rate$ OR assess$ OR measure$ OR questionnaire OR diagno$

(e.g. Fragile X syndrome, Williams Syndrome, Down Syndrome); (iv) the sample was drawn solely from a psychiatric clinical population (e.g. referrals to a psychiatric clinic). In selecting studies evaluating measures of anxiety, the following inclusion criteria was applied: (i) at least 70% of the sample were aged 17 or less with an intellectual disability/developmental delay (including those from one specific etiological group e.g. Fragile X syndrome); (ii) study reported statistical findings relating to the reliability (internal consistency, test–rest, inter-rater) and/or validity (convergent/divergent, criterion, predictive) of the anxiety measure; (iii) the paper was available in English. Evaluation studies were excluded, if: (i) the sample only included individuals with autism spectrum disorder; (ii) the study only reported psychometric statistics in relation to the assessment of mental health disorders in general, or in relation to the assessment of specific mental health disorders other than anxiety disorders (as defined by DSM-5). The reliability and validity of each selected measure was assessed using standard guidelines to interpret psychometric statistics, similar to those used by in other review papers (e.g. Hermans et al., 2011) (see Table 2 for details). 3. Results 3.1. Overview of literature review Seventy-three papers were identified from the literature search (31 from the electronic database search and 42 from the hand search) for closer review in order to determine if they met the criteria for inclusion as an anxiety prevalence study. Of these papers, 66 were excluded: 17 reported rates of mental health problems using a screening tool, 6 reported rates of mental health disorders other than anxiety disorders, 5 reported anxiety disorder diagnoses based on medical records, 36 did not meet sample requirements (e.g. autism spectrum disorder sample only, psychiatric clinic sample, more than 30% adults, fewer than 50 participants) and a further 2 did not report prevalence rates (see Fig. 1). One hundred and twenty-five papers were identified from the literature search (49 from the electronic database search and 76 from the hand search) for closer review in order to determine if they met the inclusion criteria as a study evaluating the psychometric properties of an anxiety measure. Of these papers, 104 were excluded: 5 were review papers, 55 did not meet sample requirements (10 with adult samples, 36 with autism spectrum disorder samples only, 9 with other nonintellectual disability samples), 10 studies did not include a measure of anxiety, 34 studies did not report relevant psychometric data (see Fig. 1). Table 2 Interpreting reliability and validity statistics. Internal consistency (Cicchetti, 1994) 0.05 (prevelance)

Sarphare and Aman (1996) (FSSC-R)

2 week retest (5 subscales) Child report r = 0.74–0.84, p < 0.001 (group 1) r = 0.68–0.77, p < 0.001 (group 2)

Parent–Child r = 0.54–0.59, p < 0.05 (group 1; 3 subscales) r = 0.30–0.39, p > 0.05 (group 1; 2 subscales)

Parent report 0.54–0.77, p < 0.05 (group 1; 4 sub-r = 0.28–0.13, p > 0.05 (group 2; 5 subscales) scales) 0.40, p > 0.05 (group 1, ‘Medical fears’) 0.53–0.71, p < 0.05 (group 2)

T.C. Reardon et al. / Research in Developmental Disabilities 36 (2015) 175–190

Matson, Fodstad, et al. (2009) 0.57 Childhood Symptom Inventory (CSI-4; Gadow & Sprafkin, 2002) combined with CBCL/TRF items

Fear Survey for Children With and Without Mental Retardation (FSCMR) (Ramirez & Kratochwill, 1990) Ramirez (1990)

and

Kratochwill

14–15 days retest r = 0.82 (female total score) r = 0.86 (male total score) r = 0.83 (female number of fears) r = 0.87 (male number of fears)

Ramirez et al. (1998)

Convergent FSCMR-RCMAS r = 0.51, p < 0.001

Zung Self-Rating Anxiety Scale (Zung, 1971) Masi et al. (2002)

Revised-Children Manifest Anxiety Scale (RCMAS) (Reynolds & Richmond, 1985) Ramirez et al. (1998)

Convergent FSCMR-RCMAS r = 0.51, p < 0.001

Social Anxiety Scale for Children (SASC) (La Greca et al., 1988) Sarphare and Aman (1996)

2 week retest r = 0.68, r = 0.80, p < 0.001 (group 1 & 2; FNE scale) r = 0.38, p < 0.05; 0.57, p < 0.01 (group 1 & 2; SAD scale) State Trait Anxiety Inventory for Children (STAIC) (Spielberger et al., 1973) Gullone et al. (1996)

Convergent STAIC-Trait – FSSC-II (intensity) r = 0.39, p < 0.01 STAIC-Trait FSSC-II (prevalence) r = 0.37, p < 0.01 Divergent STAIC-State – FSSC-II (intensity) r = 0.05, p > 0.05 STAIC-State – FSSC-II (prevalence) r = 0.02, p > 0.05

Pediatric Anxiety Rating Scale-Revised (PARS-R; Riddle et al., 2002, 2004) Russo-Ponsaran et al. (2014)

ICC total: 0.90 (items endorsed) ICC 5 item severity scale: 0.79 ICC 7 item severity scale: 0.85

Criterion PARS-R – Clinical Global Impression Severity for Anxiety 5 item severity scale: r = 0.97, p < 0.001 7 item severity scale: r = 0.46, p < 0.05

T.C. Reardon et al. / Research in Developmental Disabilities 36 (2015) 175–190

Convergent CBCL-Internalising r = 0.44, p < 0.001 PIMRA-Anxiety r = 0.48, p < 0.001 Zung Anxiety Scale-CBCL Anxious/Depressed r = 0.33, not significant

ICC, intraclass correlation coefficient; r, Pearson’s correlation coefficient.

185

186

T.C. Reardon et al. / Research in Developmental Disabilities 36 (2015) 175–190

DSM criteria. One study has evaluated the validity of the informant-report version of the measure in a sample of adolescents with mild–moderate ID (Masi, Brovedani, Mucci, & Favilla, 2002). The PIMRA-Anxiety Disorders subscale correlated moderately well with the CBCL Anxious/Depressed subscale (r = 0.55, p < 0.001), and slightly less well with the Zung Anxiety Self-Rating Scale (r = 0.48, p < 0.001). The Child Behaviour Checklist (CBCL; Achenbach, 1991a) and corresponding Teacher Report Form (TRF; Achenbach, 1991b) and Youth Report Form (YRF; Achenbach, 1991c) are very widely used tools within the typically developing population. Four studies evaluating the CBCL/TRF/YRF-Anxious/Depressed subscale in samples of children/adolescents with ID were identified. Douma, Dekker, Verhulst, & Koot (2006) demonstrated the YSR Anxious/Depressed subscale’s good internal consistency (0.83–0.88) among adolescents with mild–moderate ID. The same study indicated fair inter-rater reliability between parent (CBCL) and self-report (YSR), and similarly fair agreement among care staff on the CBCL was demonstrated in another sample of children/adolescents with mild ID (Embregts, 2000). The test–retest reliability of the CBCL-Anxious/ Depressed subscale was also shown to be excellent among individuals with mild ID (Embregts, 2000). Douma et al. (2006) reported convergence between the YSR and CBCL Anxious/Depressed subscale, and divergence with the other subscales. As mentioned previously, moderate convergence with the PIMRA-Anxiety Disorders scale was evidenced in adolescents with mild ID (Masi et al., 2002). Moderate convergence between CBCL/TRF and the DBC-Anxiety subscale has also been illustrated among individuals with borderline intellectual functioning and varying degrees of ID (Dekker, Nunn, et al., 2002). The subscale’s criterion validity remains to be established. Douma et al. (2006) reported that scores on the YSR-Anxious/Depressed subscale were significantly higher among adolescents with psychiatric symptoms than those without psychiatric symptoms; but this study did not examine differences in Anxious/Depressed scores among those with and without anxiety disorders. The BISCUIT-Part 2 (Matson, Wilkins et al., 2009) provides a measure of emotional problems commonly experienced by young children with developmental disabilities, and includes an Anxiety and Repetitive behaviour subscale. However, the content of the items on this 11-item subscale mostly pertain to repetitive/compulsive behaviours. Most studies examining the psychometric properties of the BISCUIT have used samples of children with autism, but one study was identified that examined the reliability of this subscale within a sample of toddlers with developmental delay without autism (Matson, Fodstad, & Mahan, 2009a). However, the only relevant reported finding related to the subscale’s internal consistency was not within the acceptable range (Cronbach’s alpha = 0.57). One study was identified that developed a measure of anxiety for use in children with Fragile X syndrome, using items from existing measures (Sullivan et al., 2007). These authors selected items from the CBCL and items from the Child Symptom Inventory (Gadow & Sprafkin, 2002) as potential behavioural equivalents of anxiety (excluding items that appear on the CBCL-DSM Oriented Anxiety problems scale). The selected items were then classified into four domains (Avoidance Behaviours-Confrontational, e.g. loses temper; Avoidance Behaviours-Non-Confrontational, e.g. avoids tasks that require a lot of mental effort; Anxiety Continuum Behaviours, e.g. shows excessive fear to specific objects or situations; Behaviour Dysregulation, e.g. talks excessively). The study then evaluated the performance of the new measure across these four domains, using the CBCL-DSM-Oriented Anxiety problems scale as a concurrent indicator of the presence of anxiety symptoms. In a sample of children with Fragile X syndrome, the internal consistency across all four domains was shown to be fair to excellent among both parent and teacher raters. The CBCL/CSI behaviour equivalent domains demonstrated good specificity, with 93.8% (parents) and 92.0% (teachers) correctly classifying those without symptoms of anxiety (measured by CBCL-DSM Anxiety problems scale). However, sensitivity was lower with only 45.5% (parents) and 77.8% (teachers) correctly identifying those true positive cases of individuals with symptoms of anxiety. 3.4.2. Evaluation of anxiety measures Two measures of fears were identified: the Fear Survey Schedule for Children-Revised (FSSC-Revised; Ollendick, 1983) and the Fear Survey for Children With and Without Mental Retardation (FSCMR; Ramirez & Kratochwill, 1990). The FSSCRevised is a self-report measure that has been modified for children with ID, and a corresponding informant report research version has also been developed. Two versions of the FSSC-Revised have been evaluated in samples of children with ID. Both versions have been shown to have excellent internal consistency (Gullone et al., 1996; King, Josephs, Gullone, Madden, & Ollendick, 1994). Gullone et al. (1996) also demonstrated high test–test reliability and Sarphare & Aman (1996) similarly found moderate to high test–retest reliability on the self-report measure. However, low to moderate test–retest reliability was reported for the parent-report version (Sarphare & Aman, 1996). Gullone et al. (1996) also only found a low correlation between the FSSC-Revised and both the Revised-Children Manifest Anxiety Scale (RCMAS) and the Trait scale of the State Trait Anxiety Inventory for Children (STAIC). However, this study did report the expected divergence between the FSSCRevised and the State scale of STAIC. The Fear Survey for Children With and Without Mental Retardation (FSCMR) is a based on a modification of the Child Fear Survey Schedule. Ramirez and Kratochwill (1990) reported high test–rest reliability for the FSCMR, and a second study reported a moderate correlation with the RCMAS (Ramirez, Nguyen, & Kratochwill, 1998). The Zung Self-Rating Anxiety Scale (Zung, 1971) is a 20 item self-report measure designed for an adult population. As described above, it has been modified for ID populations (Lindsay & Michie, 1988) and one study was identified that evaluated its use in a sample of adolescents with mild ID (Masi et al., 2002). As mentioned previously, little psychometric support for the modified Zung scale was provided in this study; a low correlation with the CBCL-Internalising score and PIMRA-Anxiety Disorders scale was reported, and no significant association with the CBCL-Anxious/Depressed subscale.

T.C. Reardon et al. / Research in Developmental Disabilities 36 (2015) 175–190

187

The Revised-Children Manifest Anxiety Scale (RCMAS; Reynolds & Richmond, 1985) and Social Anxiety Scale for Children (SASC; La Greca et al., 1988) are both self-report measures developed for typically developing children; although the former (RCMAS) is a longer measure (37 items) covering a wider range of anxiety symptoms. One study evaluating each measure in children with ID was identified. As mentioned above, a moderate correlation between the FSCMR and RCMAS was reported (Ramirez et al., 1998). The test–retest reliability of the SASC was examined and moderate to high correlations for the Fear of Negative Evaluation subscale were reported, and low–moderate for the Social Avoidance and Distress subscale (Sarphare & Aman, 1996). Again, no further reliability or validity statistics were reported. The State Trait Anxiety Inventory for Children (STAIC; Spielberger et al., 1973) provides a self-report measure of state and trait anxiety, and, as mentioned above Gullone et al. (1996) only found a low correlation with the FSSC-Revised. The Pediatric Anxiety Rating Scale-Revised (PARS-R; Riddle et al., 2002, 2004) is a clinician-rated measure that involves an interview with a parent/carer. It has been evaluated in one relevant sample of children/adolescents with Fragile X syndrome (Russo-Ponsaran, Yesensky, Hessl, & Berry-Kravis, 2014). The PARS-R includes two sections: a 61-item symptom checklist, followed by 7 (or 5) severity items in which the clinician rates the severity of symptoms (e.g. Overall Severity of Anxiety Feelings, Overall Avoidance of Anxiety-Provoking Situations, Interference with Family Relationships and/or Performance at Home). Two severity items (Overall Number of Anxiety Symptoms and Severity of Physical Symptoms of Anxiety) are excluded in the 5-item version of the severity scale. Excellent test–retest reliability in relation to both the symptom checklist items and the 5-item and 7-item severity scales were reported in a sample of children/adolescents under 17 with Fragile X syndrome (Russo-Ponsaran et al., 2014). The Clinical Global Impression Severity scale (Forkmann et al., 2011) also correlated very strongly with the PARS-R 5-item severity scale (0.97, p < 0.001); although a weaker correlation was reported for the 7-item severity scale (0.46, p < 0.05) (Russo-Ponsaran et al., 2014).

4. Discussion and conclusions Relatively few studies have examined the prevalence of anxiety disorders among children and adolescents with intellectual disabilities. Among the seven studies identified in this review, the reported prevalence rate ranged from 3% to 22%. Variation in relation to rates of specific anxiety disorders was also identified. It is important to note however that the age range used across studies varied. Consistent with studies of typically developing populations, the highest rate of separation anxiety disorder, for example, was reported in a sample of young children (5 year olds; Green et al., 2014). Interestingly, these authors reported that although rates of separation anxiety disorder decreased over time in children with ID, the reduction seemed to take longer in children with ID than typically developing children (Green et al., 2014). It is also important to note other differences between samples and methods employed across the prevalence studies. The representation of different degrees of intellectual disability varied. Some samples included individuals with borderline intellectual functioning (Baker et al., 2010; Dekker & Koot, 2003; Green et al., 2014); and the proportion of individuals with severe/profound intellectual disability within a sample ranged from 0% (e.g. Dekker & Koot, 2003) to 56% (Hassiotis & Turk, 2012). The prevalence statistic reported also varied from point prevalence (Hassiotis & Turk, 2012) to one-year prevalence (Dekker & Koot, 2003). Given the limited number of studies, and variation among samples and methods used, we need to be cautious in drawing conclusions from such a restricted evidence base. Nevertheless, the prevailing evidence has established that anxiety and the associated disorders are a significant issue within this population. Indeed, reported prevalence rates tended to be higher than reported prevalence rates of anxiety disorders in typically developing populations of children and adolescents (2–7%; Costello et al., 2003; Emerson & Hatton, 2007; Roberts et al., 2007). Furthermore, similar to typically developing populations, there appears to be variation in prevalence rates of specific anxiety disorders in children with ID at different ages. However, given the limited evidence surrounding any particular age group, further investigation is required in order to clearly establish the number of young people with ID at different ages (and stages of development) who are affected by specific anxiety disorders. Evidence surrounding the quality of measures of anxiety in children and adolescents with ID is equally sparse. Studies evaluating the psychometric properties of measures of anxiety symptoms have rarely focused on samples of children and/or adolescents with ID. Interestingly, samples of young people with autism have received more attention than those with ID; and the high rates of comorbid anxiety disorders among children/adolescents with autism are well established (Grondhuis & Aman, 2012). Nevertheless much of the focus on autism has centred on individuals with high functioning autism. In total 21 studies evaluating measures of anxiety in a sample of children/adolescents with ID were identified in this review. These studies either evaluated a broad-based measure that included a subscale measuring anxiety; or evaluated an anxiety specific measure. The evaluations focused on the extent to which a measure reliably and/or validly assesses symptoms of anxiety in the target population; however, to date, studies have not evaluated the capacity of these measures to screen for anxiety disorders in children/adolescents with ID. Among the broad-based measures identified in evaluation studies, the Developmental Behaviour Checklist (DBC) and the Nisonger Child Behaviour Rating Form (NCBRF) emerged with the strongest support for the psychometric properties of their respective subscales measuring anxiety symptoms. These broad-based measures offer the potential to assess anxiety, alongside a range of other behaviour and emotional problems. These measures also have the advantage that they are designed for the target population and therefore reflect the experience and expression of behaviour and emotional problems

188

T.C. Reardon et al. / Research in Developmental Disabilities 36 (2015) 175–190

specifically within this cohort. However, although the DBC and NCBRF may both provide a reliable and valid measure of anxiety symptoms; their capacity to screen for anxiety disorders remains unknown. There is some evidence to suggest other broad-based existing measures may have potential utility as measures of anxiety in children/adolescents with ID. The reliability and validity of the Anxious/Depressed subscale of the Child Behaviour Checklist, at least among young people with mild ID, has been established. However, as anxiety and depression symptoms are measured in a single scale, its capacity to differentiate individuals at risk for anxiety and depressive disorders, respectively, is doubtful; although this may pose a challenge for any anxiety measure for use in this population. The DSMOriented-Anxiety Problems scale of the CBCL may hold greater potential for this purpose, but its psychometric properties and screening capacity within an intellectual disability population remains to be established. Neither the Reiss Scales for Children’s Dual Diagnosis nor the Psychopathology Instrument for Mentally Retarded Adults have been sufficiently evaluated as measures of anxiety in young people with ID, with only one study meeting criteria for inclusion in this review for each measure. Thus, further work is needed to evaluate the reliability and validity of these anxiety measures in this population. The Baby and Infant Screen for Children with aUtIsm Traits’ Anxiety and Repetitive behaviour subscale also lacks an evidence base in samples without autism spectrum disorder, and importantly does not offer a measure of anxiety that is distinct from repetitive behaviour. An alternative approach was identified in one paper, in which items were selected from two existing measures in an attempt to develop a new measure of behavioural equivalents of anxiety (Sullivan et al., 2007). Such an approach to instrument development however is not well established, and the capacity of this measure to identify those with anxiety disorders proved limited. Measures specifically designed to assess anxiety have been even less well evaluated in samples of children/adolescents with ID. Most of the anxiety measures identified here had only been evaluated in one sample that met criteria for inclusion in this review (Revised-Children Manifest Anxiety Scale, Social Anxiety Scale for Children, State Trait Anxiety Inventory for Children, Pediatric Anxiety Rating Scale-Revised). The two self-report measures of fears have received a little more attention; and both with some positive results (Fear Survey for Children With and Without Mental Retardation and Fear Survey Schedule for Children-Revised). However, efforts to establish the validity of the FSSC-R have produced mixed findings, and, again, neither measure has been evaluated as a screen for anxiety disorders in children with ID. Several existing measures hold potential as reliable and valid measures of anxiety symptoms in children and adolescents with intellectual disability (e.g. the Developmental Behaviour Checklist, Nisonger Child Behaviour Rating Form, Fear Survey for Children With and Without Mental Retardation). 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.

References Achenbach, T. M. (1991a). Manual for the Child Behavior Checklist/4-18 and 1991 profile. Burlington, VT: Department of Psychiatry, University of Vermont. Achenbach, T. M. (1991b). Manual for the Teacher’s Report Form and 1991 profile. Burlington, VT: Department of Psychiatry, University of Vermont. Achenbach, T. M. (1991c). Manual for the Youth Self-Report and 1991 profile. Burlington, VT: Department of Psychiatry, University of Vermont. Achenbach, T. M., Dumenci, L., & Rescorla, L. A. (2003). DSM-oriented and empirically based approaches to constructing scales from the same item pools. Journal of Clinical Child and Adolescent Psychology, 32(3), 328–340. Aman, M. G., Tasse´, M. J., Rojahn, J., & Hammer, D. (1996). The Nisonger CBRF: A child behavior rating form for children with developmental disabilities. Research in Developmental Disabilities, 17(1), 41–57. Bailey, N. M., & Andrews, T. M. (2003). Diagnostic Criteria for psychiatric disorders for use with adults with Learning Disabilities/Mental Retardation (DC–LD) and the diagnosis of anxiety disorders: A review. Journal of Intellectual Disability Research, 47(Suppl. 1), 50–61. Baker, B. L., Neece, C. L., Fenning, R. M., Crnic, K. A., & Blacher, J. (2010). Mental disorders in five-year-old children with or without developmental delay: Focus on ADHD. Journal of Clinical Child and Adolescent Psychology, 39(4), 492–505. Bird, H. R., Shaffer, D., Prudence, F., Gould, M. S., Staghezza, B., Chen, J. Y., et al. (1993). The Columbia Impairment Scale (CIS): Pilot findings on a measure of global impairment for children and adolescents. International Journal of Methods in Psychiatric Research, 3, 167–176. Cicchetti, D. V. (1994). Guidelines, criteria, and rules of thumb for evaluating normed and standardized assessment instruments in psychology. Psychological Assessment, 6(4), 284. Cicchetti, D. V., & Sparrow, S. A. (1981). Developing criteria for establishing interrater reliability of specific items: Applications to assessment of adaptive behavior. American Journal of Mental Deficiency, 86(2), 127–137. Cooper, S. A., Melville, C. A., & Einfeld, S. L. (2003). Psychiatric diagnosis, intellectual disabilities and diagnostic criteria for psychiatric disorders for use with adults with Learning Disabilities/Mental Retardation (DC–LD). Journal of Intellectual Disability Research, 47(Suppl. 1), 3–15. Costello, E. J., Mustillo, S., Erkanli, A., Keeler, G., & Angold, A. (2003). Prevalence and development of psychiatric disorders in childhood and adolescence. Archives of General Psychiatry, 60(8), 837–844. Dekker, M. C., & Koot, H. M. (2003). DSM-IV disorders in children with borderline to moderate intellectual disability: I. Prevalence and impact. Journal of American Academy of Child and Adolescent Psychiatry, 42(8), 915–922. Dekker, M., Nunn, R., & Koot, H. (2002). Psychometric properties of the revised Developmental Behaviour Checklist scales in Dutch children with intellectual disability. Journal of Intellectual Disability Research, 46(1), 61–75. Dekker, M. C., Nunn, R. J., Einfeld, S. E., Tonge, B. J., & Koot, H. M. (2002). Assessing emotional and behavioral problems in children with intellectual disability: Revisiting the factor structure of the Developmental Behavior Checklist. Journal of Autism and Developmental Disorders, 32(6), 601–610. Dekker, M. C., Koot, H. M., van der Ende, J., & Verhulst, F. C. (2002). Emotional and behavioral problems in children and adolescents with and without intellectual disability. Journal of Child Psychology and Psychiatry, 43(8), 1087–1098. Douma, J. C., Dekker, M. C., Verhulst, F. C., & Koot, H. M. (2006). Self-reports on mental health problems of youth with moderate to borderline intellectual disabilities. Journal of the American Academy of Child & Adolescent Psychiatry, 45(10), 1224–1231. Edelbrock, C. (1985). Child Behavior Rating Form. Psychopharmacology Bulletin, 21(4), 835–837. Einfeld, S. L., & Tonge, B. J. (1995). The Developmental Behavior Checklist: The development and validation of an instrument to assess behavioral and emotional disturbance in children and adolescents with mental retardation. Journal of Autism and Developmental Disorders, 25(2), 81–104.

T.C. Reardon et al. / Research in Developmental Disabilities 36 (2015) 175–190

189

Einfeld, S. L., & Tonge, B. J. (1996). Population prevalence of psychopathology in children and adolescents with intellectual disability: II. Epidemiological findings. Journal of Intellectual Disability Research, 40(Pt 2), 99–109. Einfeld, S. L., & Tonge, B. J. (2002). Manual for the Developmental Behaviour Checklist: Primary carer version (DBC-P) & Teacher version (DBC-T) (2nd ed.). Clayton, Australia: Monash University Centre for Developmental Psychiatry and Psychology. Embregts, P. J. (2000). Reliability of the Child Behavior Checklist for the assessment of behavioral problems of children and youth with mild mental retardation. Research in Developmental Disabilities, 21(1), 31–41. Emerson, E. (2003). Prevalence of psychiatric disorders in children and adolescents with and without intellectual disability. Journal of Intellectual Disability Research, 47(Pt 1), 51–58. Emerson, E., & Hatton, C. (2007). Mental health of children and adolescents with intellectual disabilities in Britain. British Journal of Psychiatry, 191, 493–499. Esbensen, A. J., Rojahn, J., Aman, M. G., & Ruedrich, S. (2003). Reliability and validity of an assessment instrument for anxiety, depression, and mood among individuals with mental retardation. Journal of Autism and Developmental Disorders, 33(6), 617–629. Forkmann, T., Scherer, A., Boecker, M., Pawelzik, M., Jostes, R., & Gauggel, S. (2011). The Clinical Global Impression scale and the influence of patient or staff perspective on outcome. BMC Psychiatry, 11(1), 83. Gadow, K. D., & Sprafkin, J. N. (2002). Child Symptom Inventory 4: Screening and norms manual. Stony Brook, NY: Checkmate Plus. Green, S. A., Berkovits, L. D., & Baker, B. L. (2014). Symptoms and development of anxiety in children with or without intellectual disability. Journal of Clinical Child and Adolescent Psychology. http://dx.doi.org/10.1080/15374416.2013.873979 Grondhuis, S. N., & Aman, M. G. (2012). Assessment of anxiety in children and adolescents with autism spectrum disorders. Research in Autism Spectrum Disorders, 6(4), 1345–1365. Gullone, E., & King, N. J. (1992). Psychometric evaluation of a Revised Fear Survey Schedule for Children and Adolescents. Journal of Child Psychology and Psychiatry, 33(6), 987–998. Gullone, E., King, N. J., & Cummins, R. A. (1996). Fears of youth with mental retardation: Psychometric evaluation of the Fear Survey Schedule for Children-II (FSSCII). Research in Developmental Disabilities, 17(4), 269–284. Hassiotis, A., & Turk, J. (2012). Mental health needs in adolescents with intellectual disabilities: Cross-sectional survey of a service sample. Journal of Applied Research in Intellectual Disabilities, 25(3), 252–261. Hastings, R. P., Brown, T., Mount, R. H., & Cormack, K. M. (2001). Exploration of psychometric properties of the Developmental Behavior Checklist. Journal of Autism and Developmental Disorders, 31(4), 423–431. Hermans, H., & Evenhuis, H. M. (2010). Characteristics of instruments screening for depression in adults with intellectual disabilities: Systematic review. Research in Developmental Disabilities, 31(6), 1109–1120. Hermans, H., van der Pas, F. H., & Evenhuis, H. M. (2011). Instruments assessing anxiety in adults with intellectual disabilities: A systematic review. Research in Developmental Disabilities, 32(3), 861–870. Hinkle, D. E., Wiersma, W., & Jurs, S. G. (1979). Applied statistics for the behavioral sciences. USA: Houghton Mifflin Company. King, N. J., Josephs, A., Gullone, E., Madden, C., & Ollendick, T. H. (1994). Assessing the fears of children with disability using the Revised Fear Survey Schedule for Children: A comparative study. British Journal of Medical Psychology, 67(Pt 4), 377–386. La Greca, A. M., Dandes, S. K., Wick, P., Shaw, K., & Stone, W. L. (1988). Development of the Social Anxiety Scale for Children: Reliability and concurrent validity. Journal of Clinical Child Psychology, 17(1), 84–91. Lindsay, W., & Michie, A. (1988). Adaptation of the Zung Self-Rating Anxiety Scale for people with a mental handicap. Journal of Intellectual Disability Research, 32(6), 485–490. Linna, S. L., Moilanen, I., Ebeling, H., Piha, J., Kumpulainen, K., Tamminen, T., et al. (1999). Psychiatric symptoms in children with intellectual disability. European Child and Adolescent Psychiatry, 8(Suppl. 4), 77–82. Magiati, I., Chan, J. Y., Tan, W.-L.J., & Poon, K. K. (2014). Do non-referred young people with Autism Spectrum Disorders and their caregivers agree when reporting anxiety symptoms? A preliminary investigation using the Spence Children’s Anxiety Scale. Research in Autism Spectrum Disorders, 8(5), 546–558. March, J. S. (1998). Multidimensional Anxiety Scale for children manual. North Tonawanda, NY: Multi-Health Systems. Masi, G., Brovedani, P., Mucci, M., & Favilla, L. (2002). Assessment of anxiety and depression in adolescents with mental retardation. Child Psychiatry and Human Development, 32(3), 227–237. Matson, J. L., Kazdin, A. E., & Senatore, V. (1984). Psychometric properties of the psychopathology instrument for mentally retarded adults. Applied Research in Mental Retardation, 5(1), 81–89. Matson, J. L., Fodstad, J. C., & Mahan, S. (2009). Cutoffs, norms, and patterns of comorbid difficulties in children with developmental disabilities on the Baby and Infant Screen for Children with aUtIsm Traits (BISCUIT-Part 2). Research in Developmental Disabilities, 30(6), 1221–1228. Matson, J. L., Wilkins, J., Sevin, J. A., Knight, C., Boisjoli, J. A., & Sharp, B. (2009). Reliability and item content of the Baby and Infant Screen for Children with aUtIsm Traits (BISCUIT): Parts 1–3. Journal of Autism Spectrum Disorders, 3, 336–344. Matson, J. L., Belva, B. C., Hattier, M. A., & Matson, M. L. (2012). Scaling methods to measure psychopathology in persons with intellectual disabilities. Research in Developmental Disabilities, 33(2), 549–562. Merikangas, K. R., He, J. P., Brody, D., Fisher, P. W., Bourdon, K., & Koretz, D. S. (2010). Prevalence and treatment of mental disorders among US children in the 2001– 2004 NHANES. Pediatrics, 125(1), 75–81. Mircea, C. E., Rojahn, J., & Esbensen, A. J. (2010). Psychometric evaluation of Romanian translations of the Behavior Problems Inventory-01 and the Nisonger Child Behavior Rating Form. Journal of Mental Health Research in Intellectual Disabilities, 3(1), 51–65. Norris, M., & Lecavalier, L. (2011). Evaluating the validity of the Nisonger Child Behavior Rating Form – Parent Version. Research in Developmental Disabilities, 32(6), 2894–2900. Ollendick, T. H. (1983). Reliability and validity of the Revised Fear Survey Schedule for Children (FSSC-R). Behaviour Research and Therapy, 21(6), 685–692. Ramirez, S. Z., & Kratochwill, T. R. (1990). Development of the fear survey for children with and without mental retardation. Behavioral Assessment, 12, 457–470. Ramirez, S. Z., Nguyen, T., & Kratochwill, T. R. (1998). Self-reported fears in Hispanic youth with mental retardation: A preliminary study. Mental Retardation, 36(2), 145–156. Reiss, S., & Valenti-Hein, D. (1994). Development of a psychopathology rating scale for children with mental retardation. Journal of Consulting and Clinical Psychology, 62(1), 28. Reiss, S., Levitan, G. W., & Szyszko, J. (1982). Emotional disturbance and mental retardation: Diagnostic overshadowing. American Journal of Mental Deficiency, 86(6), 567–574. Reynolds, C. R., & Richmond, B. O. (1985). Revised Children’s Manifest Anxiety Scale manual. Los Angeles: Western Psychological Services. Riddle, M., Ginsburg, G., Walkup, J., Labelarte, M., Pine, D., et al. (2002). The Pediatric Anxiety Rating Scale (PARS): Development and psychometric properties. Journal of the American Academy of Child & Adolescent Psychiatry, 41(9), 1061–1069. Riddle, M. A., Ginsburg, G., Palapattu, A., & Walkup, J. (2004). Pediatric Anxiety Rating Scale-Revised (PARS-R). Baltimore, MD: John Hopkins Medical Institutions. Roberts, R. E., Roberts, C. R., & Xing, Y. (2007). Rates of DSM-IV psychiatric disorders among adolescents in a large metropolitan area. Journal of Psychiatric Research, 41(11), 959–967. Rojahn, J., Rowe, E. W., Macken, J., Gray, A., Delitta, D., Booth, A., et al. (2010). Psychometric evaluation of the Behavior Problems Inventory-01 and the Nisonger Child Behavior Rating Form with children and adolescents. Journal of Mental Health Research in Intellectual Disabilities, 3(1), 28–50. Russo-Ponsaran, N. M., Yesensky, J., Hessl, D., & Berry-Kravis, E. (2014). Feasibility, reproducibility, and clinical validity of the Pediatric Anxiety Rating ScaleRevised for Fragile X syndrome. American Journal on Intellectual and Developmental Disabilities, 119(1), 1–16. Rutter, M., Tizard, J., & Whitmore, K. (1970). Education, health and behaviour. London, UK: Longman Publishing Group. Ryall, M. R., & Dietiker, K. E. (1979). Reliability and clinical validity of the Children’s Fear Survey Schedule. Journal of Behaviour Therapy and Experimental Psychiatry, 9, 303–309.

190

T.C. Reardon et al. / Research in Developmental Disabilities 36 (2015) 175–190

Sarphare, G., & Aman, M. G. (1996). Parent-and self-ratings of anxiety in children with mental retardation: Agreement levels and test-retest reliability. Research in Developmental Disabilities, 17(1), 27–39. Spielberger, C. D., Gorsuch, R. L., & Lushene, R. E. (1973). State-Trait Anxiety Inventory for children. Palo Alto: Consulting Psychologists Press. Stromme, P., & Diseth, T. H. (2000). Prevalence of psychiatric diagnoses in children with mental retardation: Data from a population-based study. Developmental Medicine and Child Neurology, 42(4), 266–270. Sullivan, K., Hooper, S., & Hatton, D. (2007). Behavioural equivalents of anxiety in children with Fragile X syndrome: Parent and teacher report. Journal of Intellectual Disability Research, 51(1), 54–65. Tasse, M. J., & Lecavalier, L. (2000). Comparing parent and teacher ratings of social competence and problem behaviors. American Journal on Mental Retardation, 105(4), 252–259. Thaler, N. S., Kazemi, E., & Wood, J. J. (2010). Measuring anxiety in youth with learning disabilities: Reliability and validity of the Multidimensional Anxiety Scale for Children (MASC). Child Psychiatry & Human Development, 41(5), 501–514. Totsika, V., Hastings, R. P., Emerson, E., Lancaster, G. A., & Berridge, D. M. (2011). A population-based investigation of behavioural and emotional problems and maternal mental health: Associations with autism spectrum disorder and intellectual disability. Journal of Child Psychology and Psychiatry, 52(1), 91–99. Ung, D., Arnold, E. B., De Nadai, A. S., Lewin, A. B., Phares, V., Murphy, T. K., et al. (2014). Inter-rater reliability of the Anxiety Disorders Interview Schedule for DSMIV in high-functioning youth with autism spectrum disorder. Journal of Developmental and Physical Disabilities, 26(1), 53–65. van Steensel, F. J., Deutschman, A. A., & Bo¨gels, S. M. (2013). Examining the Screen for Child Anxiety-Related Emotional Disorder-71 as an assessment tool for anxiety in children with high-functioning autism spectrum disorders. Autism, 17(6), 681–692. Wigham, S., & McConachie, H. (2014). Systematic review of the properties of tools used to measure outcomes in anxiety intervention studies for children with autism spectrum disorders. PLOS ONE, 9(1), e85268. Witwer, A. N., Lecavalier, L., & Norris, M. (2012). Reliability and validity of the Children’s Interview for Psychiatric Syndromes-Parent version in autism spectrum disorders. Journal of Autism and Developmental Disorders, 42(9), 1949–1958. Zung, W. W. (1971). A rating instrument for anxiety disorders. Psychosomatics, 12(6), 371–379.