Intellectual disability refers to the presence of the inability or limitations to the cognitive process that facilitate functional learning in individuals (Patel, Apple, Kanungo, & Akkal, 2018). There are different factors that influence this limitation, and while some of the challenges can be eliminated through the provision of various interventions to facilitate learning, others are not rectifiable. Intellectual disability is a form of mental health issue that could have an impact on the behavioral aspects of the individual; hence, in most cases, an attempt to enhance intellectual capabilities is geared toward ensuring that the victims of the disability can become independent adults (Lakhan, 2015). Just like many other mental health issues, intellectual disability can be controlled effectively if there is an early diagnosis. For instance, if the supportive interventions are applied in the early childhood learning stage, it is possible to significantly improve the learning capabilities of the individual in their adulthood. The impairments that influence intellectual disability have to be identified at an early age so that therapeutic approaches can be applied to help the individual to boost their cognition (McGill, et al., 2018). Intellectual disability may also be caused by underlying mental health conditions that are treatable; hence, early diagnosis should be targeted. The World Health Organization (WHO) is among the entities that have actively called for nations to focus on the enhancement of mental health outcomes, including intellectual disabilities.
Intellectual disability is diagnosed through the positive identification of the inability to engage in cognitive functions normally, having deficits in adaptive functions and having difficulties in achieving the learning milestones associated with the development process (Pennington, McGrath, & Peterson, 2019). Normal cognitive skills are developed cumulatively, and people with a normal cognitive function are able to develop short term and long-term memory, which comes in handy in solving the normal challenges. If an individual portrays the lack of such ability, it is apparent that their cognition is challenged. For instance, if an individual has difficulty learning their first language, learning in school, and engaging in activities that require active reasoning, they are positively diagnosed with intellectual disability (Gopalan, 2016). Adaptive functions like language, memory and knowledge have to be continuously enhanced, but if this is not achieved, the individual should be taken through active diagnosis of their intellectual disability. The social processes also highlight the ability to learn. Some of the causes of intellectual disability include genetic abnormalities that cause underdevelopment to some parts of the brain, environmental factors in the early learning stages, and exposure to harmful elements that alter the neurocognitive development processes (Britt, Davies, & Daffue, 2018). Physical injuries to the brain, infections, and malignancy may also have an impact on the cognitive processes of the victim.
Intellectual Disability in Non-English Speakers
The non-English speakers in the nation are mostly refugees and asylum seekers from different parts of the world. Since the diagnosis process of the intellectual disabilities is a function of evaluating the individuals through observation and interaction with them, it is relatively difficult to identify such conditions where language barriers exist. For this reason, it is imperative to look into ways of bridging the language gap. This can be done through the engagement with translators as applied in other mental health areas. Whenever there is a client who cannot speak English, the professionals introduce translators to facilitate effective communication and to enable the assessments that require the observation of the clients during the interactions. With the non-English speaking victims, intellectual disabilities can only be identified if there is a critical focus on eliminating the language barrier. Most refugees, especially children, are exposed to environments where their mental wellness is jeopardized, and they may require various forms of therapy to help them to achieve normal cognitive development (Mimi, Kwan, & Lau, 2018). There should be a proactive approach by the mental health providers to provide culturally safe environments for non-English speakers facing intellectual disabilities. This should also be extended to the education system, whereby the models of learning should accommodate such victims of intellectual disability.
Challenges in Screening
When screening for intellectual disability, the most effective way of identifying the level of severity in the condition is through observation, interviewing, and assessing their performance in handling various tasks. This implies that there is a need for the presence of a common language of interaction between the professionals and the clients. However, when dealing with individuals who are not able to use English, the language barrier makes it relatively difficult to collect information from the clients. It is important to ensure that there is a language bridge between the client and the providers so that the extent of the condition, as well as the causes can be established. There are many clients who require translators to help the professionals to identify the best interventions to enhance the learning capabilities of the clients (Mimi, Kwan, & Lau, 2018). However, in cases where the victims are refugees who can only converse in their local dialects, getting a translator is quite difficult. This implies that the standard screening approaches may not always work with these clients. The standard assessment tools are associated with surveys, questionnaires, and interviews, as well as self-assessments that provide a clear picture of the mental wellness of the clients. However, without a common language and the inability to translate the clients’ language, the screening process has to be dependent on unconventional approaches. These approaches may not always be accurate because the professionals have to rely entirely on observations and they can only assess skillsets, with limited accuracy.
Previous Research on ID Prevalence in non-English Speakers
According to Dickerson & Dickerson (2020), there is a significantly larger number of children in non-English speaking communities that have Autism than children from English speaking families. The researchers conducted a study in Texas, where they revealed that there are many families with autistic children, but the identification of the condition is challenged because of the lack of communication channels that are effective between the victims and the providers. Most of the children are confined to their homes without any hope in getting the required mental health attention to enhance their cognitive capabilities through therapeutic approaches. Milne et al. (2017) conducted a study that revealed that children in non-English speaking families are more likely to miss out on accessing services that enhance their learning capabilities because of the lack of efforts to accommodate their unique needs. There is a clear indication that most of the interventions and assessments are designed to serve children who can communicate effectively in English, and the lack of platforms that focus on the needs of other children with language barriers implies that the outcomes of mental wellness among the victims will keep deteriorating.
Karvonen & Clark (2019) looked into the complex needs of students with intellectual disability and in the process of learning English. The students attempting to learn English as a second language, but have intellectual disabilities have unique needs in the instructional process, and they are likely to face major challenges in the learning process. This challenge is extended to all non-English children with intellectual disability because they have to learn the language so that they can access some of the interventions that have been proved to be highly effective in imparting learning. Mead & Schools (2018) provided information relating to the emotional impact of having intellectual disability in a society that uses a specific language to which the victims are not familiar. Non-English speakers are likely to be frustrated when they are exposed to learning environments where they have to first learn the official language. It is quite difficult for the current system to adapt to the needs of non-English speakers with learning challenges, but there should be efforts toward solving the issue.
Aims of the Review
This review aims to explore the prevalence rate of intellectual disability among non-English speakers. There is a clear indication that a very low number of these individuals have been identified, and it is necessary to look into the actual number of the affected members of the community. This is meant to prompt the relevant authorities to look into adopting programs that reach out to the non-English speakers in the society to boost their mental health outcomes. Additionally, the review aims at facilitating ideas for the adoption of assessment tools for intellectual disability that are effective for screening and diagnosing the conditions among non-English speakers.
Literature Search Strategy
Computerized searches of the Medline, Embase, PsychINFO and Global Health databases were conducted from inception of each database to 12 August 2020 using the Ovid SP interface. The predefined search terms together with the Boolean operators OR and AND entered into the Title field for the three searches are detailed below.
“Non-English” OR “refug*” OR “migrant*” OR “foreign national” OR “asylum seeker” OR “emigrant” OR “immigrant” OR “foreigner” OR “displaced person”, AND
“Prevalence” OR “pervasiveness” OR “incidence” OR “assess*” OR “screen*” OR “detect*” OR “identif*” OR “diagnos*”, AND
“Intellectual disabilit*” OR “learning disabilit*” OR “developmental disabilit*” OR “learning difficult*” OR “intellectual difficult*” OR “developmental difficult*” OR “learning impair*” OR “intellectual impair*” OR “developmental impair*” OR “mental retardation” OR “mental handicap”
Mental retardation was included as a search term in search 3 to allow for inclusion of older studies that may have explored prevalence or assessment tools as the definition and diagnosis of ID has changed significantly over recent years. Before the intellectual disabilities were known as intellectual disabilities, they used to be referred to as mental retardation. However, for a number of reasons, it was agreed that the term to refer to these conditions should change as the term retardation was found not to communicate dignity or respect as well as, in fact, frequently resulted in the devaluation of such persons. Reasons for adoption of intellectual disability were that the dame reflected the changed construct of disability described by the WHO and AAIDD, it aligned better with current professional practices that focus on functional behaviors and contextual factors, it is less offensive to individuals with the disability, and it is consistent with international terminology (Schalock, et al., 2007). As a result, the inclusion of mental retardation in the search ensured that all the resources that could have been published befoe there was a change of name were captured to inform the literature.
The inclusion criteria were: i) peer-reviewed journal articles in English; ii) quantitative study design; iii) non-English speaking adults diagnosed with a ID using a validated screening tool; iv) studies examining ID prevalence in non-English speaking adults; and v) studies examining assessment tools for ID in non-English speaking adults.
The exclusion criteria were: i) grey literature; ii) articles that related to ID treatment or intervention; iii) studies published before 1994; and iv) abstracts without corresponding full-length journal articles.
Learning disabilities, as intellectual disabilities used to be known, were only introduced into the DSM in 1994. The DSM introduced significant distinction between learning disabilities and the intellectual disabilities. While learning disabilities denote weaknesses in certain academic skills with reading, writing, and math being the main ones; intellectual is used to describe below-average IQ as well as lack of skills that are needed for daily living (Boat & Wu, 2015). The DSM diagnostic criteria for the two also differ. For learning disabilities, there must be persistent difficulties in reading, writing, and mathematic reasoning during formal school years, academic skills that are below the average range of scores in culturally and linguistically appropriate tests, learning difficulties, as well as individual difficulties that cannot be explained by developmental, neurological, sensory, or motor disorders. On the other hand, the DSM require for intellectual disabilities to have deficits in intellectual functioning, deficits in adaptive functioning that bar conforming to developmental and sociocultural standards, as well as the onset of these deficits during childhood (Regier, Kuhl, & Kupfer, 2013). As a result, since 1994, there have been a clear distinction between learning disorders and intellectual disabilities and thus this informed the exclusion of learning disabilities in the search criteria.
Study Identification and Selection
The PRISMA diagram (Moher, Liberati, Tetzlaff, Altman, & Group, 2009) details the process of appropriate study identification and selection (Fig 1.)
Characteristics of Included Studies
Table 1 describes the individual characteristics of the 4 studies examining prevalence of ID in non-English speakers. Table 2 describes the individual characteristics of the 3 studies examining screening tools for ID in non-English speakers.
Table 1: Study characteristics for studies looking at screening tools
|First author and publication date
||Population incl. healthcare setting
||Results incl. prevalence
|Vecchi et al., (2001)
||The Knox Cube Imitation Test (Knox, 1913) and Corsi Blocks Test
||The setting of the population is not provided adequately.
||20 adults (aged 18-42) with mean age 26.9.
||The two diagnostic tools cannot be reliably used to measure visuospatial processing.
||There is high reliability and the validity of the study from provided description.
||(1) Small sample size
|Trani et al., (2015)
||India and Nepal
||The Disability Screening Questionnaire (DSQ-34) (modified DSQ-27)
||The setting was general including the participants’ families
649 participants diagnosed with schizophrenia
647 of non-psychiatrically ill participants
53 women were recruited in Nepal
|DSQ-34 showed strong psychometric properties that indicate that it effectively discriminates between persons with and without disabilities.
||(1) Large sample size
(2) high reliability and the validity
|(1)The findings can only be generalized for the two studies under investigation
|Bousman et al., (2011)
||The Animal Fluency Test, Figure Memory Test, Hopkins Verbal Learning Test-Revised (Spanish adaptation of HVLT-R), Grooved Pegboard Test, Color Trails Tests 1 and 2, Wechsler Memory Scale-III Spatial Span, Academic Skills Assessment (9 question interview rated on a 4-point Likert format)
||Residents in a migrant farm working colonia (neighbourhood).
||21 adults (aged 17-57) with mean age 32.
||All tool other than figure learning were feasible and appropriate to administer to the population on immigrants in the region.
||(1) Used Spanish adapted forms of the assessments
(2) Used both non-verbal and verbal assessments
|(1) Small sample size
(2) Used tools to measure functional limitations in daily activities, not ID specifically
|First author and publication date
||Population incl. healthcare setting
||Results incl. prevalence
|McGrother et al., (2002)
Disability Assessment Schedule (Holmes et al., 1982)
|The Leicestershire Learning Disability Register
||206 South Asian and 2334 white adults
||3.20 per 1000 in South Asian population, 3.62 per 1000 in white population
||(1) Large sample size
|(2) The study used only one group of immigrants
|Durbin et al., (2019)
||Population-based retrospective cohort study
||Health and social services administrative data
|Prevalence of IDD was lower in newcomers than non-newcomers
||(3) Large population size
(4) High validity and reliability
|(1)The study did not specify the identity of the newcomers
|Cabieses et al., (2012)
||Chilean Popualtion-Based Survey (CASEN-2006)
||Secondary Data Analysis
||Immigrants have significantly lower prevalence of any disability
||(1)A large sample size
Immigrants are expansive.
|(1)Types of disabilities were not specified
|De Souza et al., (2013)
||American Community Survey (2016)
||Secondary Data Analysis
||5,191 (2,113 males; 3,078 females)
||Filipinos who were citizen by birth had higher odds of disability that the Filipino non-citizens
||(3) A large sample size
||(3) Concentrated on only one group of immigrants
Table 2: Study characteristics for studies looking at prevalence
Descriptive Characteristics of the Included Studies
The three studies that were used to provide the literature on screening tools had a total sample size of 690 participants. The settings for the three article varied from Mexico, India, Nepal, and one where the setting was not specified. All the studies were experimental in nature where the different screening tools were used among the participants who took part in the study. They all assessed the effectiveness of different tools used to screen for intellectual disabilities.
The articles that were used to provide literature on prevalence of intellectual disabilities among the immigrants had a total sample size in excess of 1,600,000. The settings of the studies varied from the United Kingdom, Canada, Chile, and the United States. The majority of these studies made use of secondary data on the population-based databases in the respective countries. The methods that were used for data analysis included secondary data analysis. The participants’ characteristic for the studies varied from a single racial/ethnic, or nationality to multiple racial/ethnic or nationalities as the immigrants in the different countries that were studied in the studies.
The Joanna-Briggs Institute critical appraisal tool (cite) and the Newcastle-Ottawa scale (cite) were used to evaluate the quality of the papers. Two tools were used to provide a more detailed quality appraisal of the included studies. The Joanna-Briggs Institute critical appraisal tool is a detailed checklist that appraises methodology and analysis, whereas the Newcastle-Ottawa scale has a focus on sample selection and uses a “star system”. The Joanna-Briggs Institute checklist for prevalence studies was used for the 4 studies examining prevalence of ID, and the Joanna-Briggs Institute checklist for cohort studies was used for the 3 studies examining screening tools for ID. The Newcastle-Ottawa scale was used across all 7 papers.
The review identified the Knox Cube Imitation Test (cite), the Disability Screening Questionnaire (DSQ-34) (cite) and a number of neuropsychological performance measures (the Animal Fluency Test, the Figure Memory Test, the Hopkins Verbal Learning Test-Revised, the Grooved Pegboard Test, Color Trails Tests 1 and 2, the Wechsler Memory Scale-III Spartial Span and an Academic Skills Assessment) (cite) as appropriate screening tools for ID in non-English speakers. Further details about the studies, including strengths and limitations are provided in Appendix.
The Knox Cube Imitation Test was developed to diagnose mental retardation in potential immigrants to the United States. Corsi Blocks Test was developed to be used in neuropsychological practice. The study showed that the two tools cannot be reliably used to purely measure the visuospatial processing and it was important to consider the architecture of working memory in order to suggest a more integrated functioning of the system. The concurrent tasks included articulatory suppression, spatial tapping, as well as random generation that tap the various components of working memory.
The Disability Screening Questionnaire (DSQ-34) is a strong that showed that it could be used as it had strong psychometric properties that indicated that it could effectively discriminate between people with and without disabilities including intellectual disabilities (Trani, Babulal, & Bakhshi, 2015). In the study, the tools could distinguish between the patients suffering from schizophrenia and comparative participants with no psychiatric condition in the two settings.
Tools to measure neuropsychological performance including Animal Fluency Test, Figure Memory Test, Hopkins Verbal Learning Test-Revised (Spanish adaptation of HVLT-R), Grooved Pegboard Test, Color Trails Tests 1 and 2, Wechsler Memory Scale-III Spatial Span, Academic Skills Assessment (9 question interview rated on a 4-point Likert format could also be feasibility be used to screen for intellectual disability amongst the immigrants. These tools are also appropriate to administer in populations of different settings (Bousman, Salgado, Hendrix, Fraga, & Cherner, 2011). However, figure leaning did not show significant feasibility in screening neuropsychological performance deficiency among individuals.
Prevalence of ID in Non-English Speakers
The study on the prevalence of the intellectual disability among the non-English speaking immigrants, the study revealed that the prevalence is not quite high as compared to the native populations. McGrother et al.., (2002) showed that the prevalence of intellectual disability among South Asians was 3.20 per 1000 people compared to 3.62 in 1000 people among the white population. Durbin et al., (2019) showed that the prevalence of IDD was lower amongst the newcomers in Ontario Canada compared to the non-newcomers in the same population (Durbin, et al., 2019). Cabieses et al., (2012) in the study revealed that the immigrants had significantly lower prevalence of any disability compared to the citizens (Cabieses, Pickett, & Tunstall, 2012). De Souza et al., (2013) found that among the Filipinos who were living in the United States had higher odds of disability compared to Filipino non-citizens.
Summary of Main Findings
The prevalence of intellectual disability among non-English speakers is higher than that of the English speakers. The non-English speakers in the country comprises mostly of the refugees and asylum seekers from across the globe. There have been numerous challenges in screening for the intellectual disabilities among the non-English speakers that may include among others the language barriers and lack of access to health care services (De Souza & Fuller -Thomson, 2013). There are numerous factors that may predispose the refugees and asylum seekers to mental health challenges like stress and socioeconomic challenges that limit their care access as well as their legal status that may imply that it is difficult for them to receive care in every country. As a result, it may be expected that the cases of intellectual disabilities will be higher amongst the non-English speakers compared to English speakers who have citizenship advantage (McGrother, Bhaumik, Thorp, Watson, & Taub, 2002). However, different studies that have been conducted to investigate the prevalence of intellectual disabilities among the non-English speakers have found that their prevalence for intellectual disabilities are lower compared to those of the English speakers. South Asians immigrants in the United Kingdom report lower prevalence rate (3.2 per 1,000) compared to that of white population in the country (3.62 per 1,000). Further, the prevalence of the intellectual and development disabilities is also lower among the newcomers in Ontario compared to the non-newcomers in the same region. Immigrants in Chile have significantly lower prevalence for intellectual disabilities compared to non-immigrants. Further, Filipinos staying in the United States as immigrants have lower prevalence for intellectual disabilities compared to the Filipinos who are citizens.
There are numerous assessment tools that can be used to screen for intellectual disabilities among the non-English speakers comprising of refuges and asylum seekers. Some of the tools that can be used for this purpose include the Knox Cube Imitation Test (1913), Corsi Blocks Test (2013), the Disability Screening Questionnaires (DSQ-34), The Animal Fluency Test, Figure Memory Test, Hopkins Verbal Learning Test-Revised (Spanish adaptation of HVLT-R), Grooved Pegboard Test, Color Trails Tests 1 and 2, Wechsler Memory Scale-III Spatial Span, Academic Skills Assessment (9 question interview rated on a 4-point Likert format). These assessment tools differ in the way they are applied as well as in the cognitive functional area that they seek to assess. The Disability Screening Questionnaires (DSQ-34), showed to have strong psychometric properties that can effectively discriminate between individuals with and without intellectual disabilities (Vecchi & Richradson, 2001). The variety of tools that were studied were found to be feasible and appropriate to the population of immigrants in assessing the intellectual disabilities. However, special observations were made with the Knox Cube Imitation Test (1913), Corsi Blocks Test (2013) that were found not to be very reliable as measures of visuospatial processing.
Implications for Research, Policy Makers and Clinicians
This research is very helpful to inform interventions that are geared towards helping the vulnerable populations like refugees and asylum seekers. These populations have many stressors that predispose them to mental health challenges. However, the study showed the prevalence of intellectual disabilities among these vulnerable populations are lower than those of the resident populations who are non-immigrant. However, this study did not explore the reason that the prevalence rates for intellectual disabilities are lower among these populations. As a result, the future research should seek to provide an explanation for the lower prevalence rates among the non-English speakers compared to the English speakers because these populations have stressors that should explain high cases of mental disabilities.
In practice, this study has provided understanding for the assessment tools that can be used effectively screen the non-English speakers for intellectual disabilities. There are numerous interventions that are aimed at helping the intellectual disabled people in the society. However, the interventions cannot be successful unless there is adequate screening to determine the nature and intensity of the intellectual disability. The findings of this study can be used to inform of the screening tools that can be used to screen these populations. Programs can make use of these assessment tools to understand the cognitive functional areas that the interventions should target.
Strengths and Limitations
This paper has provided update of literature. Previously there were few reviews of literature regarding the prevalence of intellectual disabilities among the non-English speakers. The study also provides a detailed analysis of intellectual disabilities screening tools that can be used to screen for intellectual disabilities among non-English speakers. The major limitation of this study is that it made use of secondary data for the prevalence of intellectual disabilities. The validity and reliability of secondary data is imported to the current study and thus impacting the reliability and validity of the current study. The intellectual disability studied in the current study is also defined in broader times and thus the screening tools that were used did not specify the cognitive functional areas that they should target.
The Non-English speaking populations have numerous challenges that impact their health outcomes like language barrier and lack of access to health care. One of the areas that they are expected to have poor health outcomes in the intellectual disabilities. The current study found that the non-English speaking populations comprising of refuges and asylum seekers do not have higher prevalence of intellectual disabilities. Various tools can also be used to screen for intellectual disabilities among the non-English speakers. The Disability Screening Questionnaires (DSQ-34), is efficient tool that can be used to tell the people with intellectual disabilities and those without.
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