Intellectual Disability Group Research Articles

Central Corneal Thickness in Children With Intellectual Disability: A Controlled Study

To evaluate the central corneal thickness (CCT) in children with intellectual disability (ID) and to determine the association between ID-related variables and CCT. A total of 77 subjects with ID and 38 healthy controls were included in the study. The subjects with ID were subdivided into mild (IQ 50-69; n = 34), moderate (IQ 35-49; n = 30), and severe (IQ <34; n = 13) groups and syndromic (n = 40) versus nonsyndromic (n = 37) distinctions. All children underwent CCT assessment by ultrasound pachymetry, in addition to complete ophthalmologic examination. Analysis of variance, chi test, and linear regression analysis were used for statistical analysis. CCT was significantly higher in the ID group (549.7 +/- 21.4 microm) than that the control group (521.6 +/- 16.9 microm; P < 0.0001). Linear regression analysis revealed that presence of syndromic etiology significantly predicted higher CCT among the individuals with ID (P < 0.0001). Children with ID have an increased CCT compared with healthy controls. Syndromic etiology is the only variable that predicts higher CCT among the individuals with ID. Although the finding of an increased CCT in children with ID is statistically significant, it is not clinically significant.

Theory of mind abilities in children with Down syndrome and non-specific intellectual disabilities: An empirical study with some educational implications

Several researchers explored the impact of cognition, language and social understanding on theory of mind abilities in typically developing (TD) children and children with intellectual disabilities (ID) (either ID of genetic origin or non-specific ID). The aim of the present study was to determine the specificity of the theory of mind deficit to different groups of children with ID. The results are in accordance with the developmental approach of similar structure hypothesis (Zigler, 1969). The findings are discussed in terms of the specificity of the etiology-related theory of mind profiles of ID groups, considering the educational and social inclusion practices.

Quality of Life of Iranian Vocational Students with and without Intellectual Disability

The purpose of the present study was to compare the attitudes of individuals with and without intellectual disability toward their quality of life. Associations between demographic variables such as sex, age, father's education, and father's occupation and quality of life were also assessed. 40 people with intellectual disability from special schools were matched with 40 people from Shiraz Vocational Teaching Center on sex, age, and fathers' careers and educations. There was no significant difference between the two groups on total Quality of Life scores, but differences were found in subscales. The groups with intellectual disability reported higher scores on the dimensions of life satisfaction, competency/productivity, and social belongingness/community integration. The normal group scored higher on empowerment/independence. In the intellectual disability group, the father's career was a better predictor of quality of life.

Sibling relationships in adults who have siblings with or without intellectual disabilities

There is relatively little research on the relationships between adults with intellectual disability and their siblings, despite the potential importance of these relationships for either individual's psychological well-being and future care roles that might be adopted by adult siblings. In the present study, sibling relationships of adults with adult siblings with ( N = 63) and without ( N = 123) intellectual disability were explored. Contact, warmth, conflict, and rivalry were measured using questionnaires available as an on-line survey. Expressed emotion was measured using the Five Minute Speech Sample over the telephone to establish an independently coded measure of criticism from the participant towards their sibling. Overall, there were few group differences in contact and sibling relationship. There was less telephone contact in the intellectual disability group, and less reported warmth in the relationship with siblings with intellectual disability although this was mainly associated with severe/profound intellectual disability. Exploratory analyses were conducted of the correlates of sibling relationships in both the intellectual disability and control groups. These analyses revealed a small number of different associations especially for conflict, which was lower when either the participant or sibling was younger in the control group but associated with relative age in the intellectual disability group.

Structural, Item, and Test Generalizability of the Psychopathy Checklist—Revised to Offenders With Intellectual Disabilities

The Psychopathy Checklist-Revised (PCL-R) is the most widely used measure of psychopathy in forensic clinical practice, but the generalizability of the measure to offenders with intellectual disabilities (ID) has not been clearly established. This study examined the structural equivalence and scalar equivalence of the PCL-R in a sample of 185 male offenders with ID in forensic mental health settings, as compared with a sample of 1,212 male prisoners without ID. Three models of the PCL-R's factor structure were evaluated with confirmatory factor analysis. The 3-factor hierarchical model of psychopathy was found to be a good fit to the ID PCL-R data, whereas neither the 4-factor model nor the traditional 2-factor model fitted. There were no cross-group differences in the factor structure, providing evidence of structural equivalence. However, item response theory analyses indicated metric differences in the ratings of psychopathy symptoms between the ID group and the comparison prisoner group. This finding has potential implications for the interpretation of PCL-R scores obtained with people with ID in forensic psychiatric settings.

Student–Teacher Relationship Stability Across Early School Years for Children With Intellectual Disability or Typical Development

Student-teacher relationships of 37 children with moderate to borderline intellectual disability and 61 with typical cognitive development were assessed from child ages 6-8 years. Student-teacher relationship quality was moderately stable for the typical development group, but less so for the intellectual disability group. At each assessment these relationships were poorer for children with intellectual disability. Child behavior problems consistently predicted more conflict, whereas social skills predicted more closeness. Accounting for these child characteristics reduced the status group difference to nonsignificance. Earlier student-teacher relationships predicted subsequent changes in child behavior problems and social skills. Student-teacher relationships in the intellectual disability group were significantly lower for children in regular than special classes by age 8.

Reliability and validity of a physical capacity evaluation used to assess individuals with intellectual disabilities and mental illness

Physical capacity evaluations (PCEs) are important and frequently offered services in work practice. This study to investigate the reliability and validity of the National Taiwan University Hospital Physical Capacity Evaluation (NTUH PCE) on a sample of 149 participants consisted of three groups: 45 intellectual disability (ID), 56 mental illness (MI), and 48 no disability (ND). Intraclass correlation coefficient (ICC), Cronbach alpha, and one-way ANOVA were calculated where appropriate. Results indicated that most subtests of the NTUH PCE had good to excellent test-retest reliability (ICC, 0.75-0.95), with the exception of subtests of the position tolerance section for ID and MI groups and the hand coordination section for the ND group. Good internal consistency was shown on strength, mobility, and hand coordination sections (alpha, 0.96, 0.90, and 0.95, respectively), with the exception of the position tolerance section (alpha=0.37). The known group validity of the NTUH PCE in people with disabilities was satisfactory. In conclusion, although some improvements are needed in some subtests, the NTUH PCE is suitable for measuring physical work-related abilities of people with disabilities.

A comparative neuropsychological test battery differentiates cognitive signatures of Fragile X and Down syndrome

Standardised neuropsychological and cognitive measures present some limitations in their applicability and generalisability to individuals with intellectual disability (ID). Alternative approaches to defining the cognitive signatures of various forms of ID are needed to advance our understanding of the profiles of strengths and weaknesses as well as the affected brain areas. To evaluate the utility and feasibility of six non-verbal comparative neuropsychological (CN) tasks administered in a modified version of the Wisconsin General Test Apparatus (WGTA) to confirm and extend our knowledge of unique cognitive signatures of Fragile X syndrome (FXS) and Down syndrome (DS). A test battery of CN tasks adapted from the animal literature was administered in a modified WGTA. Tasks were selected that have established or emerging brain-behaviour relationships in the domains of visual-perceptual, visual-spatial, working memory and inhibition. Despite the fact that these tasks revealed cognitive signatures for the two ID groups, only some hypotheses were supported. Results suggest that whereas individuals with DS were relatively impaired on visual-perceptual and visual-spatial reversal learning tasks they showed strengths in egocentric spatial learning and object discrimination tasks. Individuals with FXS were relatively impaired on object discrimination learning and reversal tasks, which was attributable to side preferences. In contrast, these same individuals exhibited strengths in egocentric spatial learning and reversal tasks as well as on an object recognition memory task. Both ID groups demonstrated relatively poor performance for a visual-spatial working memory task. Performance on the modified WGTA tasks differentiated cognitive signatures between two of the most common forms of ID. Results are discussed in the context of the literature on the cognitive and neurobiological features of FXS and DS.

Dose Requirements for Propofol Anaesthesia for Dental Treatment for Autistic Patients Compared with Intellectually Impaired Patients

We had clinical grounds to suspect that patients with autism had greater propofol requirements during dental procedures than patients with intellectual impairment without autism. This hypothesis was tested by an audit of a standard anaesthetic technique. The audit was approved by our Hospital Ethics Committee. We compared the propofol requirements and effect using a standardised protocol during dental treatment in 56 autistic patients (age range three to 35 years) and 56 intellectually impaired patients (age range four to 42 years). Patients in each disability group were divided into three subgroups by age: six years or younger, seven to 19 years and 20 years or older. Combative patients received oral midazolam premedication, other patients received a single intravenous bolus of midazolam at induction. Otherwise, standardised propofol boluses and infusion were the only anaesthetic agents used. The propofol infusion rates of the intellectually impaired group showed significant decline with age (propofol rate of requirement mg x kg(-1) x h(-1), mean [SD]): < six years 13.6 (3.6), seven to 19 years 9.5 (3.0) (P = 0.008 cf < six years group), > 19 years group 8.5 (2.4) (P = 0.001 cf < six years group). The propofol requirement was greater in the autism group than in the intellectual disability group, and the proportion of the cases where bolus propofol administration was needed after induction was significantly higher in the autistic patient group than in the intellectually impaired patients (P < 0.002). This suggests that autistic patients have greater propofol requirements for anaesthesia during ordinary dental treatment compared with intellectually impaired patients.

Sensorimotor Impairments and Strategies in Adults with Intellectual Disabilities

Adults with intellectual disabilities (ID) show a greater tendency toward deconditioning and having a sedentary lifestyle than their peers without disabilities. The aim of this study was to characterize sensorimotor deficits through coordination tests and during static and dynamic balance. Eight tasks that involved the integration of hand movements with visual information were used here, as well as the Posture Scale Analyzer system to examine postural stability. During static and dynamic standing tests with the eyes closed, the postural stability of people with ID was accompanied by a small sway rate. In the ID group, the frontal plane movements were significantly larger (p>.05) than the sagittal plane movements. The participants with ID showed a significantly lower score than the control group in all the sensorimotor tests. Our observations on balance and coordination capabilities might have significance for understanding the mechanisms underlying movement dysfunction in adults with ID and offer some new approaches for their possible prevention.

A Comparison of Feeding and Mealtime Problems in Adults with Intellectual Disabilities with and Without Autism

Feeding and mealtime behavior problems are an area of concern for those with autism spectrum disorders (ASD) because of their impact on daily functioning, as well as the potential for causing severe medical conditions (e.g., poor nutrition, choking, aspiration) and even death. Due to the importance of this topic for proper diagnosis and treatment planning, a better understanding of these behaviors in persons with ASD and intellectual disabilities (ID) is important. Participants in this study were 60 adults with ASD and ID (group 1) or ID only (group 2). Individuals with ASD and ID evinced more behaviorally-based feeding problems, such as food selectivity and refusal related difficulties relative to their peers with ID alone as assessed with the Screening Tool of fEeding Problems (STEP). Those with ID only had more feeding skill difficulties than persons with ASD and ID. Overall, the ASD and ID group evinced more, and more severe feeding and mealtime problems. Implications of these data are discussed.

The relationship of dementia prevalence in older adults with intellectual disability (ID) to age and severity of ID

Previous research has shown that adults with intellectual disability (ID) may be more at risk of developing dementia in old age than expected. However, the effect of age and ID severity on dementia prevalence rates has never been reported. We investigated the predictions that older adults with ID should have high prevalence rates of dementia that differ between ID severity groups and that the age-associated risk should be shifted to a younger age relative to the general population. A two-staged epidemiological survey of 281 adults with ID without Down syndrome (DS) aged 60 years; participants who screened positive with a memory task, informant-reported change in function or with the Dementia Questionnaire for Persons with Mental Retardation (DMR) underwent a detailed assessment. Diagnoses were made by psychiatrists according to international criteria. Prevalence rates were compared with UK prevalence and European consensus rates using standardized morbidity ratios (SMRs). Dementia was more common in this population (prevalence of 18.3%, SMR 2.77 in those aged 65 years). Prevalence rates did not differ between mild, moderate and severe ID groups. Age was a strong risk factor and was not influenced by sex or ID severity. As predicted, SMRs were higher for younger age groups compared to older age groups, indicating a relative shift in age-associated risk. Criteria-defined dementia is 2-3 times more common in the ID population, with a shift in risk to younger age groups compared to the general population.

Enhancing visual search abilities of people with intellectual disabilities

This study aimed to evaluate the effects of cueing in visual search paradigm for people with and without intellectual disabilities (ID). A total of 36 subjects (18 persons with ID and 18 persons with normal intelligence) were recruited using convenient sampling method. A series of experiments were conducted to compare guided cue strategies using either motion contrast or additional cue to basic search task. Repeated measure ANOVA and post hoc multiple comparison tests were used to compare each cue strategy. Results showed that the use of guided strategies was able to capture focal attention in an autonomic manner in the ID group (Pillai's Trace = 5.99, p < 0.0001). Both guided cue and guided motion search tasks demonstrated functionally similar effects that confirmed the non-specific character of salience. These findings suggested that the visual search efficiency of people with ID was greatly improved if the target was made salient using cueing effect when the complexity of the display increased (i.e. set size increased). This study could have an important implication for the design of the visual searching format of any computerized programs developed for people with ID in learning new tasks.

The effect of intellectual disability on the adherence of child witnesses to a “story grammar” framework

Background This study examined the ability of 78 children (aged 9–12 years) with an intellectual disability (ID) to provide a narrative account of a staged event they had participated in four days earlier.Method The children were interviewed using open‐ended questions. The quality of their responses (using a story grammar framework) was compared with that of two control groups: mainstream children matched for mental and chronological age.Results While the children with an ID and those matched for mental age provided narratives of similar length and used similar proportions of each story grammar element, the ID group was less likely than both control groups to provide a narrative account at all. Among those children with an ID who did provide a narrative account, their accounts included proportionately fewer story grammar elements than those of both control groups.Conclusion Children with an ID are disadvantaged as witnesses with respect to their ability to provide a detailed and coherent narrative account of events under optimal investigative interviewing conditions.

Perceptual-motor coordination in persons with mild intellectual disability

Background. There is limited experimental evidence to support the view that individuals with intellectual disabilities (ID) have a deficit in motor control. This work is a first attempt to evaluate their motor coordination.Purpose. The study assessed the relationship between cognitive ability and sensorimotor integration. The clinical hypothesis is that adults with ID fall below non-ID adults in motor skills that involve hand-eye coordination.Method. A group of 42 adults with ID (ID group) was compared to 48 age-matched typical adults (TA) using a mixed experimental design (‘Task’ as the within-subjects factor and ‘Group’ as the between-subjects factor). Participants performed the following tests twice: Box-and-Blocks, 25-Grooved-Pegboard, Stick Catching and overhead Beanbag-Throw. Pearson correlations and ANOVAs were used to test the hypothesis (p ≤ 0.05).Results. As expected, TA outperformed the ID group in all tests regardless of the hand used during for the assessment. However, TA individuals scored significantly better with one hand (i.e., the preferred and dominant hand) as opposed to persons with ID, who exhibited no hand preference. Test-retest correlations among the first and second assessment scores yielded moderate-strong coefficients, depending on the type of test (Box-and-Blocks = 0.92 and 0.96, 25-Grooved-Pegboard = 0.69 and 0.83, Stick-Catching = 0.88 and 0.94, Beanbag-Throw = 0.58 and 0.91 for ID and TA, respectively).Discussion. Difficulties in the integration of perceptual information into motor action may result in inadequate solutions to daily motor problems. As it stems from our results, intellectual disability relates to inability to integrate visual inputs and hand movements. In people with mild ID such inability is observed using both hands (i.e., they show no hand preferences). Poor perceptual-motor coordination might have a functional significance in that it may lead to exclusion from vocational and recreational activities, and a decreasing competence of ADL. Assessing coordination in adults with ID may contribute to understanding the nature of the ID condition and may encourage an early rehabilitation.

Recognition and Language in Low Functioning Autism

The hypothesis that a pervasive impairment of declarative memory contributes to language impairment in low functioning autism (LFA) was tested. Participants with LFA, high functioning autism (HFA), intellectual disability (ID) without autism, and typical development (TD) were given two recognition tests and four tests of lexical understanding. It was predicted that recognition would be impaired in the LFA group relative to the HFA and TD groups but not the ID group, and that recognition would correlate with lexical knowledge in the LFA group but none of the other groups. These predictions were supported except that the HFA group performed more similarly to the LFA group than expected, a finding interpreted in terms of selectively impaired episodic memory.

Predictive validity of the PCL‐R for offenders with intellectual disability in a high security hospital: Treatment progress

Background Among mainstream offenders, the severe personality disorder of psychopathy has considerable importance as a construct. The disorder has long been associated with failure to make treatment progress. Previous work has identified that psychopathy as a disorder occurs in samples of offenders with intellectual disability (ID), and suggests that the Psychopathy Checklist – Revised (PCL‐R: Hare, 1991, 2003) as a measure of the disorder has adequate reliability and validity (Morrissey et al., 2005). The present study aimed to compare the predictive power of the PCL‐R in relation to treatment progress with a more general assessment of violence risk, the HCR‐20 (Webster, Douglas, Eaves, & Hart, 1997).Method A sample of 73 residents in a high security intellectual disability service, who had previously been assessed using the PCL‐R and the HCR‐20, were followed up at 2 years post‐assessment, and their outcome determined in terms of two distinct dichotomous variables reflecting definite positive treatment progress and definite negative treatment progress respectively.Results In line with predictions, the PCL‐R Total score and Factor 1 score (Interpersonal and Affective aspects of psychopathy) and the HCR‐20 Total score were significantly inversely associated with a positive move from high to medium security hospital conditions within 2 years of assessment. However against prediction, the PCL‐R Total score had incremental validity over the HCR‐20. The PCL‐R Total and Factor 1, but not the HCR‐20 Total score, were also significantly associated with negative treatment progress in terms of a move to more restricted treatment conditions.Conclusion Psychopathy, and in particular its interpersonal and affective manifestations, is a construct which appears to be associated with indirect measures of treatment progress in this high security ID group. However, caution should be applied in the use of a construct with potentially negative connotations in an already devalued population.

Central Corneal Thickness in Individuals With Intellectual Disabilities

To assess central corneal thickness (CCT) values in individuals with intellectual disabilities (ID). The study group was made up of 25 participants with ID (mean age, 36.9 +/- 8.7 years). The control group was made up of 25 healthy individuals (mean age, 37.1 +/- 10.1 years) with normal intellectual capacity and without any systemic or intraocular pathology. CCT value was measured by ultrasound pachymetry. Ten consecutive measurements were made at the center of the cornea of each eye. In the ID group, mean CCT value was 554.0 +/- 39.7 microm in the right eye and 556.8 +/- 38.7 microm in the left eye. In the control group, mean CCT value was 535.7 +/- 24.2 microm in the right eye and 536.5 +/- 24.8 microm in the left eye. CCT value in the ID group was significantly greater than in the control group for both right (P < 0.05) and left eyes (P < 0.02). CCT should be kept in mind during measurements of intraocular pressure (IOP) in individuals with ID because their CCTs may be greater than those in the general population.

Sensorimotor development and dysregulation of activity in young children with autism and with intellectual disabilities

Dysregulation of activity linked with development was analysed in 12 children with intellectual disabilities (ID) and in 12 children with autism (ASD) matched on their developmental age (18 months). The “Batterie d’Evaluation du Développement Cognitif et Social” [Adrien, J. L. (1996). Autisme du jeune enfant. Développement psychologique et régulation de l’activité [ Autism in the young child: Psychological development and behavioral regulation]. Paris: Expansion Scientifique Française] and the «Regulation Disorders Evaluation Grid» [Adrien, J. L., Rossignol-Deletang, N., Martineau, J., Couturier, G., & Barthélémy, C. (2001). Regulation on cognitive activity and early communication development in young autistic, mentally retarded, and young normal children. Developmental Psychobiology, 39(2), 124–136] were used. T-test comparisons, partial correlation controlling for chronological age and clusters analyses by cases were completed. Children with ASD showed more dysregulation than ID children and both groups showed different patterns of specific dysregulation disorders. Dysregulation of activity was linked to development but correlations were much more numerous and intense within ASD group compared to ID group.

A measure of food seeking in individuals with Prader–Willi syndrome

Individuals with Prader-Willi syndrome (PWS), a chromosome 15 genetic disorder, often have a significant preoccupation with food and problem behaviour related to food seeking is often prevalent. In the present study, we compared how individuals with PWS responded on a survey regarding the acceptability of food in various locations that varied according to degree of appropriateness for human consumption (e.g. food on a plate, food in a garbage can). For a subgroup of participants, we observed how they actually responded when placed in a room with food items placed in the same locations depicted in the survey. In the first part of the study, three groups (25 typically developing individuals, 7 individuals with intellectual disability (ID), and 19 individuals with PWS) responded to a visual survey to determine the degree of acceptability of food items in various locations (e.g. on a table near a hairbrush, on the floor behind a toy box, in a trash can). In the second part of the study, these food items (popcorn, jelly beans) were placed in the 12 locations described above. Nine individuals diagnosed with PWS (deletion type) and three individuals with ID were given some break time in the room for 15 min. The amount of food consumed, the time spent food seeking, and time spent interacting with materials were measured. Results of the survey indicated that the PWS group differed significantly with regard to how they responded on the survey from the typically developing group, but did not differ significantly from the ID group. Results of the food seeking observations indicated that only three individuals with PWS ate a significant number of items. The three individuals did not differ from the rest of the group according to IQ or compulsivity score; however, they had significantly lower body mass index (BMI) scores and were younger than the other participants. The findings from the survey indicate that individuals with PWS are able to discriminate the appropriateness of eating items in more or less contaminated areas; however, the amount of time spent seeking food and the amount of food covertly consumed appeared to depend more directly on age and BMI.