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Intellectual Disability

The scope of this page is centralized content about individuals with an intellectual disability (ID) and associated communication difficulties across the life span.


See ASHAs Intellectual Disability evidence map for summaries of the available research on this topic.

Intellectual Disability

The definitions of intellectual disability (ID) and related terminology have evolved over time to reflect the legal and social gains made by individuals with such a disability and their families. See Changes in Services for Persons With Developmental Disabilities: Federal Laws and Philosophical and Perspectives and Federal Programs Supporting Research and Training in Intellectual Disability. These changes reflect the movement from institutionalization to inclusive practices, self-advocacy, and self-determination. There has also been the movement toward recognizing fundamental communication rights of people with severe disabilities. A Communication Bill of Rights—originally developed by the National Joint Committee for the Communication Needs of Persons with Severe Disabilities (NJC) in 1992 and updated in 2016—recognizes the right of all people to effective communication (NJC, 1992; Brady et al., 2016).

One of the major shifts in the early 1980s was a move toward person-first language, reflecting the idea that the disability does not define the person. Terms like individuals with intellectual disability have replaced the older terms of mentally retarded persons or the mentally retarded, and definitions of ID have changed from being strictly intelligence quotient (IQ)–based to including strengths in adaptive behavior (Schalock, Luckasson, & Shorgren, 2007).

ID is characterized by

  • significant limitations in intellectual functioning (e.g., reasoning, learning, and problem solving);
  • significant limitations in adaptive behavior (i.e., conceptual, social, and practical skills in everyday life); and
  • onset in childhood (before the age of 18 years; American Association on Intellectual and Developmental Disabilities [AAIDD, 2013]).

This definition of ID balances limitations with an equal emphasis on skills. Consequently, language and philosophy concerning ID now focuses on levels of support necessary to maximize an individual's ability, rather than strictly on deficits in functioning.

The AAIDD definition is consistent with the diagnostic criteria for Intellectual Disability (Intellectual Developmental Disorder) in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5; American Psychiatric Association [APA], 2013). Severity levels (mild, moderate, severe, and profound), as defined in DSM-5, are based on adaptive functioning in the conceptual, social, and practical domains.

Limitations in adaptive functioning in specific skill areas are a necessary criterion for diagnosis under the AAIDD and DSM-5 definitions. The World Health Organizations (WHO, 2001) International Classification of Functioning, Disability and Health (ICF) and the ICF Children and Youth Version (WHO, 2007) recognize activity and participation limitations in addition to impairments in body functions and structures.

Developmental Disability

ID is a subset of developmental disability (DD). DD is defined as follows:

  • A severe, chronic disability in an individual 5 years of age or older
  • Onset before 22 years of age
  • Results in substantial functional limitations in three or more areas of life activity (self-care, receptive and expressive language, learning, mobility, self-direction, capacity for independent learning, economic self-sufficiency
    (Developmental Disabilities Assistance and Bill of Rights Act, 2000)

    Lifelong, early-onset conditions that result in substantial functional limitations—but not necessarily concomitant intellectual limitations—include autism spectrum disorder (ASD) or cerebral palsy (although many individuals with these conditions do, in fact, have ID). Individuals with these diagnoses who have age-level cognitive skills would be considered to have DD without ID.

    Co-occurring Conditions and Disorders

    Individuals with ID are a heterogeneous group, and communication skills can vary due to factors such as severity, co-occurring conditions, and other behavioral, emotional, and social factors.

    Conditions that either commonly co-occur with—or are fully comorbid with—ID include but are not limited to ASD, cerebral palsy, Down syndrome, fetal alcohol syndrome, and Fragile X syndrome. Other conditions that may also co-occur with ID include anxiety disorder, attention-deficit/hyperactivity disorder, depressive and bipolar disorder, impulse-control disorder, and major depressive disorder (APA, 2013). See Communication Characteristics: Selected Populations With an Intellectual Disability for general communication characteristics of individuals with these most common conditions associated with ID.

    Associated Health Conditions

    Individuals with ID may have more health problems than others in the general population, often as a result of inadequate health care, limited access to quality services (Krahn, Hammond, & Turner, 2006; van Schrojenstein Lantman-de Valk & Noonan Walsh, 2008), and communication limitations (Gentile, Cowan, & Smith, 2015).

    Associated health conditions with a higher prevalence in individuals with ID include:

    • anxiety disorders (Oeseburg, Dijkstra, Groothoff, Reijneveld, & Jansen, 2011);
    • hearing loss (Herer, 2012);
    • heart conditions (Patja, Molska, & Iivanainen, 2001);
    • obesity-related problems (Rimmer, Yamaki, Lowry, Wang, & Vogel, 2010);
    • seizure activity (Oeseburg et al., 2011); and
    • visual impairment (Warburg, 2001). 

    Greater attention could be devoted to special health needs of individuals with disabilities as a regular part of medical training (Sullivan et al., 2011). Addressing health inequalities as well as providing adequate health care and medical training can improve quality of life and increase longevity in individuals with ID.

    Incidence of ID refers to the number of new cases identified in a specified time period. Prevalence of ID refers to the number of people who are living with the condition in a given time period. The incidence/prevalence data in this section pertain to U.S.-based populations.

    The determination of incidence and prevalence of ID is complicated because researchers of ID do not use the same operational definition when selecting and identifying individuals with ID. In some cases, an IQ cutoff score is used (e.g., 70) as a criterion for diagnosis, whereas in other cases, the diagnostic criteria are more qualitative in nature (e.g., onset in childhood with limitations in adaptive behavior and intellectual functioning). Variations in study design, terminology definitions, sample size and characteristics, and diagnostic tools can also affect incidence and prevalence data. For example, some study authors use the terms intellectual disability and developmental disability interchangeably, the latter of which can include conditions like ASD and developmental language disorder. Keep these factors in mind when reviewing the incidence and prevalence data below.

    Overall Population

    • A 2011 meta-analysis of international studies found the ID prevalence of individuals across the life span to be 10.37/1000 or 1.04% (Maulik, Mascarenhas, Mathers, Dua, & Saxena, 2011).
    • A follow-up meta-analysis of international studies, extending the work of Maulik et al. (2011), found the ID prevalence of children/adolescents and adults to range from .05 to 1.55% (McKenzie, Milton, Smith & Ouellette-Kuntz, 2016).

    Children and Adolescents: Overall

    • Data from the 2011 meta-analysis of international studies found the ID prevalence of children and adolescents to be 18.3/1000 or 1.83% (Maulik et al., 2011).
    • The follow-up meta-analysis of international studies reported the prevalence range for children and adolescents to be from 0.22 to 1.55% (McKenzie et al., 2016).
    • Data from the 2006-2010 National Health Interview Survey indicated that ID prevalence in children under 18 years of age in the United States was 0.5% (Schieve et al., 2012).
    • The 2009/2010 National Survey of Children With Special Health Care Needs revealed that approximately 5.8% of children aged 2-17 years in the United States had an ID.
    • In a 2010 U.S. Census Bureau study, ID was diagnosed in approximately 154,000 (0.4%) children under 15 years of age (Brault, 2012).
    • During the 2014-2015 school year, approximately 0.12% of 3- to 5-year-old children and 0.62% of 6- to 21-year-old students who were served under the Individuals with Disabilities Education Act, Part B, had a diagnosis of ID (U.S. Department of Education, 2015).

    Children and Adolescents: Gender

    • Based on data from the 2011 meta-analysis of international studies, the female-to-male ratio of children and adolescents with ID varied between 0.4 and 1.0 (i.e., four to 10 females with ID for every 10 males with the condition; Maulik et al., 2011; Maulik, Mascarenhas, Mathers, Dua, & Saxena, 2013).

    Children and Adolescents: Co-Morbidities

    • The Autism and Developmental Disabilities Monitoring (ADDM) Network of the Centers for Disease Control (CDC) noted a prevalence of 4 per 1,000 children aged 8 years with ASD who also had ID (Christensen et al., 2016).
    • The ADDM report on the prevalence of co-occurring ASD and ID also revealed a greater male-to-female prevalence ratio of 3.7 males to 1.0 female in children 8 years old (Christensen et al., 2016).
    • Data from the 2009-2010 Annual Survey of Deaf and Hard of Hearing Children and Youth revealed an ID prevalence of 15.5% in children who are deaf with ASD and 8.2% in children who are deaf without ASD (Szymanski, Brice, Lam, & Hotto, 2012).

    Children and Adolescents: Co-Morbidity And Race/Ethnicity

    • Co-morbid ASD and ID was significantly lower in non-Hispanic White children (3.3 per 1,000) than non-Hispanic Black children (5.8 per 1,000) who were 8 years old (Christensen et al., 2016).

    Adults: Overall

    • Data from the 2011 meta-analysis of international studies found the ID prevalence of adults to be 4.94/1,000 or .49% (Maulik et al., 2011).
    • The follow-up meta-analysis of international studies found the ID prevalence of adults to range from .05 to .08% (McKenzie et al. 2016).
    • A study by the U.S. Census Bureau revealed that approximately 1.2 million (0.5%) civilian, noninstitutionalized adults had ID in 2010 (Brault, 2012).

    Adults: Gender

    • Based on data from the 2011 meta-analysis of international studies, the female-to-male ratio of adults with ID varied between 0.7 and 0.9 (i.e., seven to nine females with ID for every 10 males with the condition; Maulik et al., 2011; Maulik et al., 2013).

    Defining Characteristics

    Individuals with ID have intellectual deficits as well as deficits in adaptive functioning in the conceptual, social, and practical domains (APA, 2013).

    Deficits in Intellectual Functions

    • Language development
    • Reasoning
    • Problem solving
    • Planning
    • Abstract thinking
    • Judgment
    • Academic learning
    • Learning from experience

    Deficits in Adaptive Functioning

    • Failure to meet developmental and sociocultural standards for personal independence and social responsibility
    • Limited functioning in one or more daily life activities (e.g., communication, social participation, and independent living) across settings–in the home, school, work, and community).

    The level of support needed for adaptive functioning (i.e., performance of basic life skills) determines the severity level for ID. According to the DSM-5 (APA, 2013), the signs and symptoms of adaptive functioning deficits across domains may include:

    Conceptual Domain
    • Slow language development (children learn to talk later, if at all)
    • Slow development of pre-academic skills
    • Difficulties in academic learning (reading, writing, mathematics)
    • Difficulty understanding concepts of time and money
    • Problems with abstract thinking (concrete approach to problem solving)
    • Difficulties in executive function (i.e., planning, strategizing, priority setting, cognitive flexibility)
    • Problems with short-term memory
    • Difficulties with functional use of academic skills such as money management and time management
    Social Domain
    • Limitations in language and communication skills
      • More concrete and less complex spoken language (if used), compared with peers
      • Limited vocabulary and grammatical skills
      • Receptive language that may be limited to comprehension of simple speech and gestures
      • Communication that may occur through nonspoken means only—such as gestures, signs, facial expressions, and other forms of augmentative and alternative communication (AAC)
    • Social Skills
      • Immature social judgment and decision making
      • Difficulty understanding peer social cues and social rules
      • Emotional and behavioral regulation difficulties that may adversely affect social interactions
    Practical Domain
    • Requiring different levels of support for daily life activities such as
      • Personal care
      • Complex tasks (e.g., shopping, transportation, care organization, meals, money management)
      • Employment
      • Health care and legal decisions
      • Household tasks
      • Recreational skills

    Communication Patterns

    Individuals with ID and associated language and communication disorders may demonstrate signs and symptoms of spoken and written language disorders across the domains of phonology, morphology and syntax, semantics, and pragmatics. See spoken language disorders and written language disorders for information related to language comprehension and production, multiple modes of communication (e.g., AAC), and behavioral difficulties as well as social and emotional problems experienced by individuals with language disorders.

    Individuals with ID are a heterogeneous group; communication abilities vary and may be nonsymbolic (e.g., gestures, vocalizations, problem behaviors) and/or symbolic (e.g., words, signs, pictures). See Communication Characteristics: Selected Populations With an Intellectual Disability for examples of typical communication patterns of individuals with ASD, cerebral palsy, Down syndrome, fetal alcohol syndrome, and Fragile X syndrome, all of which most commonly co-occur with ID.

    There are prenatal, perinatal, and postnatal causes of ID. Some prenatal causes (e.g., environmental influences) are preventable. Genetic causes account for 45% of ID (Batshaw, Roizen, & Lotrecchiano, 2013). Down syndrome is the largest genetic cause of ID, and Fragile X syndrome is the largest inherited cause of ID. Fetal alcohol syndrome is the largest environmental cause of ID.

    Prenatal

    • Genetic syndromes (e.g., Down syndrome and Fragile X syndrome)
    • Inborn errors of metabolism
    • Brain malformation (e.g., microcephaly)
    • Maternal disease (e.g., placental disease)
    • Environmental influences (e.g., alcohol, other drugs, toxins, teratogens)

    Perinatal

    • Labor and delivery–related events (leading to neonatal encephalopathy)
    • Anoxia at birth

    Postnatal

    • Hypoxic ischemic injury
    • Traumatic brain injury
    • Infections
    • Demyelinating disorders
    • Seizure disorders (e.g., infantile spasms)
    • Severe and chronic social deprivation
    • Toxic metabolic syndromes and intoxications (e.g., lead, mercury)

    Cross-cultural attitudes and beliefs may influence some individuals perceptions about ID and its causes (Allison & Strydom, 2009; Scior, 2011).

    Although speech-language pathologists (SLPs) do not diagnose ID themselves, they play a key role in assessing the communication skills of individuals with ID, and they may be part of a team making a differential diagnosis between ID and ASD or other conditions.

    SLPs also play a role in enhancing adaptive communication functioning, as many of the adaptive skill areas rely on communication abilities. For example, conceptual skills include receptive and expressive language, reading, and writing; social skills include interpersonal skills, following laws, and problem solving; and practical skills include following routines, using the telephone, and using social media.

    The professional roles and activities in speech-language pathology include clinical/educational services (assessment, planning, and treatment); prevention and advocacy; and education, administration, and research. See ASHA's Scope of Practice in Speech-Language Pathology (ASHA, 2016b).

    Appropriate roles for SLPs include the following:

    • Provide information to individuals and groups known to be at risk for ID, to their family members, and to individuals working with those at risk;
    • Screen individuals who may have hearing, speech, language, communication, and/or swallowing difficulties and determine the need for further assessment and/or referral for other services;
    • Conduct a culturally and linguistically relevant and age-appropriate assessment of speech, language, communication, and swallowing, using formal and informal tools;
    • Assess the need for AAC services and supports;
    • Determine eligibility for speech and language services;
    • Refer to other professionals to rule out other conditions, determine etiology, and facilitate access to comprehensive services;
    • Promote early identification of DDs and help to implement services to maximize the potential of young children;
    • Partner with families in assessment and intervention with individuals with ID;
    • Participate as a member of the school planning team (e.g., whose members include parents, teachers, special educators, counselors, and psychologists) to determine appropriate educational services;
    • Make decisions about the management of communication deficits in persons with ID;
    • Develop treatment plans for speech and language services, including social language goals and goals for assisting with self-regulatory and social interactive functions to enable participation in daily activities and curriculum to as great an extent as possible;
    • Provide treatment, document progress, and determine appropriate dismissal criteria;
    • Counsel persons with ID and their families regarding communication-related issues and provide education aimed at enhancing communication development and preventing further complications related to ID;
    • Educate other professionals on the needs of persons with ID and the role of SLPs in diagnosing and managing communication deficits of those with ID;
    • Collaborate with parents, teachers, caregivers, job coaches, peers, and others to promote communication development and use in individuals with ID;
    • Serve as an integral member of a team working with individuals with ID and their families/caregivers and, when appropriate, considering transition planning;
    • Support students with ID throughout their school years and in postsecondary education settings;
    • Support individuals with ID in vocational and community settings;
    • Consult and collaborate with other professionals, family members, caregivers, and others to facilitate program development and to provide supervision, evaluation, and/or expert testimony, as appropriate;
    • Remain informed of research in the area of ID and helping advance the knowledge base related to the nature and treatment of ID;
    • Advocate for individuals with ID and their families at the local, state, and national levels; and
    • provide quality control and risk management.

    As indicated in the Code of Ethics (ASHA, 2016a), SLPs who serve individuals with ID should be specifically educated and appropriately trained to do so.

    See the Assessment section of the Intellectual Disability evidence map for pertinent scientific evidence, expert opinion, and client/caregiver perspective.

    Screening

    SLPs screen for hearing, speech, language, communication, and swallowing problems. Screening does not result in a diagnosis of a disorder but, rather, determines the need for further assessment and/or referral for other services. Screening may not be a needed step for individuals with ID, particularly those with more severe limitations in intellectual or adaptive functioning. For these individuals, a comprehensive assessment is likely to be the first step.

    Screening typically includes

    • gathering information from parents, teachers, and co-workers regarding concerns about an individuals language(s) and skills in each language;
    • conducting a hearing screening to rule out hearing loss as a possible contributing factor to language difficulties;
    • administering formal screening assessments that have normative data and/or cutoff scores and that have demonstrated evidence of adequate sensitivity and specificity;
    • using informal measures, such as those designed by the clinician and tailored to the population being screened (e.g., preschool, school-age/adolescence, adult);
    • observing speech production, language comprehension and production, social communication, and literacy skills in natural environments; and
    • conducting a screening of swallowing function.

    Screening may result in recommendations for

    • complete audiologic assessment;
    • comprehensive language assessment;
    • comprehensive speech sound assessment, if the speech sound system is not appropriate for the individuals age and/or linguistic community;
    • comprehensive literacy assessment; and
    • referral for other assessments or services.

    Comprehensive Assessment

    Collaboration and Teaming

    Assessment for individuals with ID involves multiple professionals due to the varying and far-reaching needs across developmental domains. Team models may be multidisciplinary, interdisciplinary, or transdisciplinary (see collaboration and teaming).

    The particular collaborative team model that is selected depends on the needs of the individual with ID. Team members determine strengths and limitations in adaptive functioning and collaboratively determine the levels of supports needed across conceptual, social, and practical domains.

    The role of SLPs and audiologists is to assess the individuals speech, language, and hearing skills. Assessments are sensitive to cultural and linguistic diversity and address components within the ICF (WHO, 2001) framework, including body structures/functions, activities/participation, and contextual factors. Findings from the communication and hearing assessments should be analyzed in the context of findings from other professionals (e.g., psychologist) for whom an ID diagnosis is within their purview.

    Components of a Comprehensive Assessment

    Both formal and informal assessment approaches can be used. Formal testing may be required if diagnosis or eligibility have yet to be determined for a child at risk for, or suspected of, a DD. Informal testing may be most useful to determine the childs achievement of specific developmental milestones. See assessment tools, techniques, and data sources that may be used in a comprehensive communication assessment. Dynamic assessment may be used to identify nonsymbolic and symbolic communication behaviors and to evaluate individual learning potential (Pea, 1996; Snell, 2002).

    The comprehensive assessment may include the following, depending on the age and functioning of an individual with ID and his or her needs:

    • Case history, including medical, educational, and vocational status as well as teacher, caregiver, employer, and client/patient perspectives on the problem.
    • Interview with family members about communication during daily routines.
    • Review of auditory, visual, motor, and cognitive status, including hearing screening.
    • Assessment of
      • nonsymbolic (e.g., gestures, vocalizations, problem behaviors) and/or symbolic (e.g., words, signs, pictures) communication;
      • play;
      • social interaction and social communication;
      • spoken language (listening and speaking);
      • written language (reading and writing);
      • speech production;
      • oral motor skills;
      • swallowing; and
      • fluency.
    • Assessment for AAC and/or other assistive technology.
    • Identification of the potential for effective intervention strategies and compensations.

    Details regarding the components of a comprehensive assessment are available on the following Practice Portal pages:

    For individuals with ASD and ID, also see autism spectrum disorder and social communication disorder for relevant assessment considerations based on individual needs.

    Information provided in Communication Characteristics: Selected Populations With an Intellectual Disability may be useful in putting together an assessment protocol to document an individual performance profile. For example:

    • Children with Down syndrome often have a specific deficit in expressive syntax relative to semantics. They also have difficulty with speech production due to low muscle tone and characteristic facial dysmorphlogy (Berglund, Eriksson, & Johansson, 2001; Roberts, Price, & Malkin, 2007). Therefore, children with Down syndrome may require a detailed evaluation of syntactic production relative to comprehension along with a speech intelligibility inventory.
    • Individuals with Fragile X syndrome often have pragmatic language difficulties (Abbeduto & Sterling, 2011). They would benefit from a detailed evaluation of social communication relative to language structure and function.

    Assessment may result in

    • diagnosis of a communication disorder or delay, secondary to ID;
    • description of the characteristics and severity of the communication disorder or delay;
    • determination of performance variability as a function of communicative situations/contexts;
    • identification of possible hearing problems;
    • recommendations for intervention and support;
    • recommendation of a communication system (e.g., low-tech or speech-generating device [SGD]);
    • referral to other professionals as needed (e.g., physician, physical therapist, occupational therapist, psychologist, or counselor);
    • recommendations for support for parents, caregivers, teachers, and employers; and
    • recommendations for support for transitions (e.g., early intervention into school age; school age into work place).

    Family-Centered Practices

    Persons with ID and their families are integral to the assessment process and are pivotal decision makers in determining specific goals and objectives and how clinical services should be provided following the assessment.

    Families offer an important and unique knowledge base about the strengths, challenges, and needs for the individual with ID. They provide useful information about communication skills during daily routines. They also identify valued life outcomes for their children (e.g., being safe and healthy, having a home, establishing meaningful relationships, having choices and control, and creating opportunities for meaningful activities across environments; Giangreco, 1990). Ultimately, the decision about specific goals and objectives rests with the family and the person with ID, recognizing that the individual family circumstances and values are central to the decision-making process.

    See family-centered practice for general guidelines.

    Cultural and Linguistic Factors

    Individuals with ID commonly experience stigmatization, discrimination, and health inequalities across cultures (Allison & Strydom, 2009). Because of this, some family members may not be willing to seek services, even when such services are readily available.

    Linguistic factors may influence an assessment protocol when working with individuals who are multilingual. Careful consideration of language history (e.g., quality and duration of exposure to different languages) and linguistic abilities in all languages is necessary in the evaluation. See bilingual service delivery, cultural competence, and collaborating with interpreters for additional information.

    Eligibility for Services

    Individuals with ID of all ages are eligible for SLP services because enhancement of communication skills is needed to function effectively, regardless of age or cognitive level relative to communication abilities. Eligibility is an area that has continued to evolve as the rights of individuals with ID have been increasingly well-recognized. In fact, the NJC emphasizes that there are no prerequisites for communication (NJC, 2002, 2003).

    Beginning with the Developmental Disabilities Services and Facilities Act of 1970 (PL 91-517), eligibility rules for service delivery for ID have undergone widespread change (e.g., Hauber, 1984; Kohlenberg, Mack, & Brown, 1996; Whitney-Thomas, Timmons, Gilmore, & Thomas, 1999).

    Categorically applying a priori criteria in making decisions on eligibility for services is not consistent with the law and IDEA regulations (IDEA, 2004). These a priori criteria cause concern when applied without regard to individual needs. They include discrepancies between cognitive and communication functioning (cognitive referencing); diagnosis; absence of prerequisite cognitive or other skills; and failure to benefit from previous communication services and supports. See NJC (2002, 2003) for information related to a priori criteria. Also see ASHAs resource page on cognitive referencing.

    Cognitive referencing is a particular concern when applied to individuals with disabilities in general and to individuals with ID in particular (Casby, 1992; Cole, Dale, & Mills, 1990; Cole & Fey, 1996; Notari, Cole, & Mills, 1992). Cognitive referencing rests on the assumption that language skills cannot improve beyond cognitive ability. Relevant research indicates that language intervention benefits children with ID even when no language–cognition discrepancy exists (D. Carr & Felice, 2000; Cole et al., 1990; Warren, Gazdag, Bambara, & Jones, 1994).

    The absence of prerequisite cognitive or other skills for determining eligibility is also of concern for individuals with ID. There are no prerequisites for communication supports and services, including the use of AAC (Romski & Sevcik, 2005). For example, some individuals with ID may be good candidates for immediate introduction of symbolic communication goals that target acquisition and use of words or AAC symbols. For individuals with extremely limited functional communication, other short-term goals may be equally appropriate (e.g., broader communication goals such as turn-taking and social participation, both of which involve nonsymbolic modes such as gesturing).

    For information about eligibility for services in the schools, see eligibility and dismissal in schools, IDEA Part B Issue Brief: Individualized Education Programs and Eligibility for Services, and 2011 IDEA Part C Final Regulations.

    Adolescents and Adults With ID

    Individuals with ID continue to develop communication skills beyond the school years (e.g., Cheslock, Barton-Hulsey, Romski, & Sevcik, 2008). As the person with ID reaches adolescence and adulthood, his or her communication and functional needs change. For example, the teen years place a premium on peer interactions, use of social media, and communication skills needed to optimize acceptance and relationship development.

    Individuals transitioning from school to vocational settings will need communication skills specific to the work setting (e.g., talking with co-workers and supervisors, interacting with customers).

    SLPs work to maximize the participation and independence of individuals with ID as they experience life transitions that place new demands on communication. The speech-language assessment will need to incorporate an evaluation of skills needed to support the individuals changing communication needs.

    ID and Hearing Loss

    An increased prevalence of hearing loss has been reported in individuals with ID as compared with the general population. For example, considerable rates of conductive hearing loss have been reported in children with Down syndrome (e.g., Hess, Rosanowski, Eysholdt, & Shuster, 2006; Park, Wilson, Stevens, Harward, & Hohler, 2012), and Herer (2012) found that the prevalence of hearing loss in noninstitutionalized adults with ID was higher than for individuals in the general population and that the hearing loss occurred at a much younger age.

    Therefore, early detection of hearing loss and routine monitoring are essential for ensuring positive communication outcomes. The comprehensive assessment includes a hearing screening and referral for a complete audiological assessment, if hearing concerns are indicated.

    See permanent childhood hearing loss and hearing loss–beyond early childhood for more information.

    Challenging Behaviors

    Comprehensive assessment of individuals with ID involves assessment of the function of challenging behaviors, also known as problem behaviors. Common challenging behaviors include aggressive, disruptive, self-injurious, and stereotypic behaviors.

    Challenging behaviors can function as a means to gain attention (social reinforcement), express wants or needs (tangible reinforcement), indicate frustration or a desire to avoid a nonpreferred activity or event (escape-avoidance), or gain sensory input (sensory reinforcement).

    Understanding these broad functions of nonspeech modes can lead to greater understanding of the potential communication functions of challenging behaviors (e.g., Reichle & Wacker, 1993) and development of responsive interventions. This knowledge serves as the basis for replacing problem behaviors with more appropriate communication skills, including AAC, that would serve the same functions (see functional communication training [FCT] in the Treatment section).

    Differential Diagnosis

    SLPs need to differentiate between ID and other disorders and conditions (e.g., spoken language disorders and hearing loss) whose communication problems—particularly when severe—can be mistakenly attributed to ID (e.g., late language emergence and ASD).

    Developmental Delay

    Developmental delay (DD) is commonly used as a temporary diagnosis in young children at risk for ID. It indicates a failure to achieve age-appropriate developmental milestones (Petersen, Kube, & Palmer, 1998). More severe impairments are more likely to result in early identification of ID (Daily, Ardinger, & Holmes, 2000).

    Often, the first sign of a developmental problem—including in milder forms of ID—is delayed language development. Therefore, SLPs may need to help make a differential diagnosis between (a) late language emergence and (b) ID or another DD.

    ASD

    SLPs may receive referrals for children with communication delays or deficits and limitations in social functioning. These behaviors may signal ASD, ID, or other conditions. The SLP may be part of a team making a differential diagnosis between ID and ASD or a diagnosis of comorbidity. Diagnosis of ID or ASD may be difficult because of the similarities and co-morbidity between the two conditions.

    Commonalities between ASD and ID include:

    • onset during the developmental period;
    • deficits in nonspoken and verbal communication skills;
    • limitations in social participation; and
    • attention and academic difficulties.

    Differences between ASD and ID include the following:

    • Individuals with ID have deficits in intellectual functioning, by definition; however, individuals with ASD have a range of intellectual abilities, from having an IQ within normal limits to having severe IQ limitations.
    • Individuals with ID usually develop skills slower than do their typically developing peers, but some follow patterns of typical development; those with ASD may not follow the typical developmental progression of skills across domains (e.g., communication and social interaction).
    • Research shows that individuals with ASD have difficulty with theory of mind (i.e., understanding the perspective of others), regardless of their level of cognitive functioning; these difficulties are more severe in individuals with ASD than in individuals with ID alone (Yirmiya, Erel, Shaked, & Solomonica-Levi, 1998).

    See the Treatment section of the Intellectual Disability evidence map for pertinent scientific evidence, expert opinion, and client/caregiver perspective.

    Each individual with ID has a unique profile, based on his or her level of language functioning as well as functioning in areas related to language and communication, including hearing, cognitive level, speech production skills, and emotional status. Intervention considers coexisting strengths and needs in all areas to ensure individualized treatment and supports.

    Research supports the provision of communication intervention for individuals with ID (Sevcik & Romski, 2016; Snell et al., 2010). As indicated by AAIDD (2013), a persons level of life functioning will improve if appropriate personalized supports are provided over a sustained period (Additional Considerations section, para. 2). The goal of treatment is to minimize the potential debilitating effects of disabilities on clients and their families and to maximize the likelihood of desirable outcomes.

    Treatment Principles

    Communication intervention focuses on the context of interactions and includes individuals that persons with ID encounter in their natural environments. SLPs ensure that intervention provides ample opportunities for communication and incorporates a variety of language functions (e.g., greeting, commenting, requesting); multiple partners; different forms and modalities [e.g., speech, AAC]; and varied communication contexts [e.g., home, educational, recreational, vocational, and community settings]). Treatment approaches typically encompass a variety of techniques and approaches (Goldstein, 2006).

    SLPs help ensure that communication partners recognize and respond to communication attempts and build on the interests, initiations, and requests of persons with ID. When involving others in intervention activities, SLPs foster an appreciation for the importance of language in future learning and functioning.

    See Treatment Principles for Individuals With an Intellectual Disability.

    Treatment Targets and Contexts

    Communication intervention is sensitive to cultural and linguistic diversity and addresses components within the ICF (WHO, 2001) framework, including body structures/functions, activities/participation, and contextual factors (personal and environmental).

    Depending on assessment results, age, severity, etiology, and communication and related needs, intervention for individuals with ID may address the areas of

    • early communication skills (e.g., pointing, turn-taking, joint attention);
    • social interaction and play;
    • pragmatic conventions (spoken and nonspoken) for communicating appropriately in varied situations;
    • speech production;
    • spoken and written language for social, educational, and vocational functions, with an emphasis on participation in specific activities identified as problematic for the individual;
    • literacy;
    • increased complexity of spoken and written language for more effective communication;
    • contextual factors that influence the individuals relative success or difficulty in those activities;
    • compensatory communication techniques and strategies, including the use of AAC or other assistive technology; and
    • feeding and swallowing.

    SLPs prioritize treatment targets on an individual basis, focusing on those that have the greatest potential for improving communication.

    Treatment programs often incorporate training of communication partners to support the individuals language comprehension and expression. Training can include use of communication strategies, cuing techniques, and/or assistive technology.

    Interprofessional collaboration also has the potential to improve communication skills. For example, an exercise physiologist and an SLP may work together to improve respiratory support, which can in turn enhance speech production and intelligibility.

    See ASHA's Preferred Practice Patterns for a more detailed outline of the major components of communication intervention for individuals across the life span (ASHA, 2004).

    Treatment Modes/Modalities

    Treatment modes and modalities are technologies or other support systems that can be used in conjunction with or in the implementation of various treatment options. For example, video-based instruction can be used in peer-mediated interventions to address social skills and other target behaviors.

    Augmentative and alternative communication (AAC)—supplementing, or using in the absence of, natural speech and/or writing with aided (e.g., picture communication symbols, line drawings, Blissymbols, and tangible objects) and/or unaided (e.g., manual signs, gestures, and finger spelling) symbols. Aided symbols require some type of transmission device; unaided symbols require only the body to produce. Aided AAC includes speech-generating communication devices (Beukelman & Mirenda, 2013). See ASHA's Practice Portal page on Augmentative and Alternative Communication.

    Activity schedules/visual supports—activity schedules/visual supports include objects, photographs, drawings, or written words that act as cues or prompts to help individuals complete a sequence of tasks/activities, attend to tasks, transition from one task to another, or behave appropriately in various settings. Written and/or visual prompts that initiate or sustain interaction are called scripts. Scripts are often used to promote social interaction but can also be used in a classroom setting to facilitate academic interactions and promote academic engagement (Hart & Whalon, 2008).

    Computer-based instruction—the use of computer technology (e.g., iPad) and/or computerized programs to teach communication and social skills (e.g., Bernard-Opitz, Sriram, & Nakhoda-Sapuan, 2001; Neely, Rispoli, Camargo, Davis, & Boles, 2013).

    Video-based instruction (also called video modeling)—an observational mode of teaching that uses video recordings to provide a model of the target behavior or skill. Video recordings of desired behaviors are observed and then imitated by the individual (Darden-Brunson, Green, & Goldstein, 2008). The learners self-modeling can be videotaped for later review.

    Treatment Options

    Below are brief descriptions of treatment options commonly used to address communication problems associated with ID. The treatment modes/modalities described above (e.g., AAC) may be used to implement these treatment options. Intervention for individuals with ID typically incorporates a variety of options and techniques in combination. This list is not exhaustive, and the inclusion of any specific treatment approach does not imply endorsement from ASHA.

    SLPs determine which options are appropriate by taking into consideration the individuals age and language profile and communication needs, factors related to language functioning, the presence of co-existing conditions, cultural background and values, and available research evidence.

    Other portal pages can serve as useful resources for treatment options, depending on the etiology for the ID. On the ASHA Practice Portal, see the treatment sections of autism spectrum disorder, spoken language disorders, and social communication disorder.

    Behavioral Interventions

    Behavioral interventions and techniques (e.g., different reinforcement, prompting, fading, and modeling) are designed to reduce problem behaviors and teach functional alternative behaviors using the basic principles of behavior change. These methods are based on behavioral/operant principles of learning; they involve examining the antecedents that elicit a certain behavior, along with the consequences that follow that behavior, and then making adjustments in this chain to increase desired behaviors and/or decrease inappropriate ones. Behavioral interventions range from one-to-one, discrete trial instruction to naturalistic approaches.

    Applied behavior analysis (ABA)—a treatment approach that uses principles of learning theory to bring about meaningful and positive change in behavior. ABA techniques have been used to help build a variety of skills (e.g., communication, social skills, self-control, and self-monitoring) and help generalize these skills to other situations. The techniques can be used in both structured (e.g., classroom) and everyday (e.g., family dinnertime) settings and in one-on-one or group instruction. ABA has been used for individuals with ID, particularly those who also have ASD (e.g., Spreckley & Boyd, 2009).

    Intervention is customized based on the individuals needs, interests, and family situation. ABA techniques are often used in intensive, early intervention (before age 4 years) programs to address a full range of life skills (e.g., Frea & McNerney, 2008). Intensive programs total from 25 to 40 hours per week for 1 to 3 years. Qualifications for providing ABA therapy may vary by state; check with your state, as this may affect reimbursement.

    Environmental arrangement—a technique that involves arranging the environment to encourage communication (Halle, 1988; McCormick, Frome Loeb, & Schiefelbusch, 2003). The idea is to increase interest in the environment and set the occasion for communication. The SLP can build on the individuals desire to request and comment on aspects of the environment using strategies such as putting interesting materials in sight but out of reach; sabotaging the situation with missing elements or providing inadequate portions; and setting up choice-making, unexpected, or silly situations.

    Functional communication training (FCT)—a behavioral intervention program that combines the assessment of the communicative functions of problem behavior with ABA procedures to teach alternative responses. Problem behaviors can be eliminated through extinction and replaced with alternate, more appropriate forms of communicating needs or wants. FCT can be used across a range of ages and regardless of cognitive level or expressive communication abilities (E. G. Carr & Durand, 1985).

    An FCT approach has been used with students with ID to replace challenging behaviors with appropriate communication alternatives (Brady & Halle, 1997; Martin, Drasgow, Halle, & Brucker, 2005; Schmidt, Drasgow, Halle, Martin, & Bliss, 2014). The first step is the definition of the challenging behavior and the antecedent and consequent variables hypothesized to motivate them (Dunlap & Fox, 1999 ; Lucyshyn, Kayser, Irvin, & Blumberg, 2002; Schwartz, Boulware, McBride, & Sandall, 2001). Second, the SLP uses this information to identify and teach simple and potentially more efficient communication skills that serve the same functions. Finally, one may expand on those skills and ensure that appropriate communication skills are used effectively in different contexts and that the challenging behavior is extinguished.

    Incidental teaching—a teaching technique that uses behavioral procedures to teach elaborated language; naturally occurring teaching opportunities are provided based on the individuals interests. Following the individuals lead, attempts to communicate are reinforced as these attempts get closer to the desired communication behavior (McGee, Morrier, & Daly, 1999). Incidental teaching requires initiation by the individual, which serves to begin a language teaching episode. If the person does not initiate, an expectant look and a time delay might be sufficient to prompt language use. The clinician can prompt with a question (e.g., What do you want?) or model a request (e.g., Say: I need paint.).

    Milieu therapy—a range of methods (including incidental teaching, time delay, and mand-model procedures) that are integrated into a childs natural environment. It includes training in everyday environments and during activities that take place throughout the day, rather than only at therapy time. Milieu language teaching and other related procedures offer systematic approaches for prompting children to expand their repertoire of communication functions and to use increasingly complex language skills (Kaiser, Yoder, & Keetz, 1992; Kasari et al., 2014).

    Time delay—a behavioral method of teaching that fades the use of prompts during instruction. For example, the time delay between initial instruction and any additional instruction or prompting is gradually increased as the individual becomes more proficient at the skill being taught. Time delay can be used with individuals regardless of cognitive level or expressive communication abilities (e.g., Liber, Frea, & Symon, 2008).

    Peer-Mediated/Implemented Treatment

    Peer-mediated/implemented treatment approaches incorporate peers as communication partners for children with disabilities in an effort to minimize isolation, provide effective role models, and boost communication competence. Typically developing peers are taught strategies to facilitate play and social interactions; interventions are commonly carried out in inclusive settings where play with typically developing peers naturally occurs (e.g., preschool setting). The following examples may be used for children with ID, based on individual communication needs.

    Learning Experiences and Alternative Program (LEAP)—a multifaceted program for preschool children with ASD and their parents (Hoyson, Jamieson, & Strain, 1984; Strain & Hoyson, 2000). LEAP uses a variety of strategies and methods, including ABA, peer-mediated instruction, self-management training, prompting, and parent training. LEAP is implemented in a classroom setting consisting of children with ASD and typically developing peers and is designed to support child-directed play.

    Circle of Friends—a treatment approach that uses the classroom peer group to improve the social acceptance of a classmate with special needs by setting up a special group or circle of friends. The focus is on building behaviors that are valued in everyday settings. The application of skills to new and appropriate situations is reinforced as naturally as possible as such situations occur (Whitaker, Barratt, Joy, Potter, & Thomas, 1998).

    Integrated play groups—a treatment model designed to support children of different ages and abilities with ASD in mutually enjoyed play experiences with typical peers and siblings. Small groups of children play together under the guidance of an adult facilitator. The focus is on maximizing the childs potential and his/her intrinsic desire to socialize with peers (Wolfberg & Schuler, 1993).

    Treatment Considerations

    Target Behaviors for Specific Populations

    Selection of target behaviors for individuals with ID has benefited from an increased understanding of the specific communication deficits associated with various diagnoses, especially the most studied populations—Down syndrome and ASD. A variety of approaches may be selected based on individual strengths and needs.

    Consider the following examples:

    • For children with Down syndrome, interventions have tended to focus on improving intelligibility through speech and alternative modes of communications (Girolametto, Weitzman, & Clements-Baartman, 1998; Kay-Raining Bird, Gaskell, Babineau, & MacDonald, 2000; Kumin, Council, & Goodman, 1999; Layton & Savino, 1990; Warren & Yoder, 1998; Yoder & Warren, 2001).
    • For children with ASD, interventions typically focus on social communication skills (e.g., Goldstein, English, Shafer, & Kaczmarek, 1997; Kaiser, Hancock, & Nietfeld, 2000; Pierce & Schreibman, 1995; Smith & Camarata, 1999; Stevenson, Krantz, & McClannahan, 2000; Thiemann & Goldstein, 2004). Peer-mediated intervention approaches have shown particular success with young children.
    Transitioning Youth

    Individuals with ID may experience challenges in acquiring the skills necessary for independent living and achieving success in postsecondary education/training programs, employment settings, and social situations. They need continued support to facilitate a successful transition to adulthood. SLPs are involved in transition planning and may be involved to varying degrees in other support services beyond high school.

    See transition youth.

    Aging Adults

    The SLP helps maximize independent functioning in aging adults. Adults with ID experience the same age-related health problems and functional decline observed in the general elderly population (Lazenby-Paterson & Crawford, 2014). However, the aging process may be premature in adults with ID as compared with the general population (e.g., Lin, Wu, Lin, Lin, & Chu, 2011).

    For example, individuals with Down syndrome may be at higher risk for earlier onset of dementia when compared with the general population (Burt et al., 2005; Hawkins, Eklund, James, & Foose, 2003). Even when dementia is not taken into account, speech and language skills may begin to decline in adults with ID from about the age of 50 (Roberts et al., 2007). If adults with ID seek speech and language services because of new communication concerns, SLPs will need to consider the possibility that the individual is experiencing mild cognitive impairment, a condition characterized by subtle cognitive deficits that may lead to dementia (see dementia).

    Most healthy adults will not experience problems with eating, drinking, and swallowing, despite age-related changes in the muscles used for feeding and swallowing (Lazenby, 2008). However, some adults with ID—particularly those with psychomotor impairments or other comorbid conditions that affect feeding and swallowing—may experience dysphagia-related problems as they age (Lazenby-Paterson & Crawford, 2014).

    Individuals With Challenging Behaviors

    When individuals with ID are taught communication skills that serve efficiently and effectively as alternative behaviors, reductions in challenging behaviors result (Kurtz, Boelter, Jarmolowicz, Chin, & Hagopian, 2011).

    Identifying and treating behaviors early in development may promote appropriate communication using alternative modes and prevent negative long-term consequences. Replacing challenging behaviors with appropriate and increasingly sophisticated communication skills has the potential to facilitate growth in academic achievement and improve social relationships and vocational outcomes.

    Identifying the function of challenging behaviors can be a complex task in itself. For example, the motivation for a specific challenging behavior can vary based on context (task vs. leisure contexts; Haring & Kennedy, 1990). SLPs are encouraged to consider a potentially preventive approach by teaching communication skills that serve multiple functions (Wacker, Berg, Harding, & Asmus, 1996).

    SLPs have an essential role in educating team members about the communication functions of such behaviors and developing methods for replacing them with other forms of communication behavior.

    Cultural and Linguistic Factors

    Cultural differences in the attitudes, beliefs, and perceptions of individuals with ID are well documented within the United States and in other countries (Allison & Strydom, 2009; Scior, 2011; WHO, 2010). This information is important because it affects service delivery and the interaction between the SLP and the family. Although there has been a global movement to encourage deinstitutionalization of individuals with ID and improve access to quality care and social integration, this is not yet a reality in all countries.

    Cultural perspectives affect communication and the way care is provided. SLPs need to (a) be aware of culturally associated beliefs about the cause of ID, (b) provide person-centered care, (c) build working relationships with caregivers, and (d) address communication barriers (Allison & Strydom, 2009).

    Service Delivery

    See the Service Delivery section of the Intellectual Disability evidence map for pertinent scientific evidence, expert opinion, and client/caregiver perspective.

    In addition to determining the type of speech and language treatment that is optimal for individuals with ID, SLPs consider other service delivery variables—including format, provider, timing, and setting—that may affect treatment outcomes. Service delivery decisions are made based on the individuals communication needs relative to his or her family, community, school, or work setting.

    Format

    Format refers to the structure of the treatment session (e.g., group vs. individual; direct and/or consultative) provided.

    Service delivery options include home-based, pull-out, classroom-based (e.g., push-in), and collaborative consultation. The pull-out model continues to be the predominant service delivery option for SLP practice across populations and ages. However, exclusive use of this model with persons with ID is rarely appropriate. Failure to generalize has been a commonly cited drawback to traditional pull-out models of service delivery (Cirrin & Penner, 1995; Nelson, 1998).

    Provider

    Provider refers to the person offering the treatment (e.g., SLP, trained volunteer, caregiver).

    Recommended practices follow a collaborative process that involves a multifaceted team including families, caregivers, persons with disabilities, and professionals. These teams establish and coordinate services that are family centered, culturally appropriate, comprehensive, and compassionate, and that produce meaningful life outcomes. Involved partners may include parents, siblings, grandparents, friends, and acquaintances in the home; teachers, classmates, paraprofessionals, and others in the school; employers, job coaches, and fellow workers in vocational settings; and a variety of conversational partners in community settings (recreational facilities, churches and synagogues, stores, etc.).

    Models of teaming require varying degrees of collaboration and engage participants in the establishment of a joint purpose, shared goals, and an organized approach to implementing these goals. See collaboration and teaming.

    Timing

    Timing refers to the scheduling of intervention relative to the diagnosis.

    The importance of early intervention for children who are at high risk for communication disorders cannot be overstated. For children with ID and other DDs, intervention that focuses on factors influencing development may improve outcomes in overall cognitive development and social competence (e.g., Guralnick, 2005; Ludlow & Allen, 1979; Mahoney & Perales, 2005; Ramey & Ramey, 1998).

    Setting

    Setting refers to the location of treatment (e.g., home, community-based, work).

    There are several advantages to providing services in the everyday contexts of persons with ID. More contextually based models are consistent with the natural environments philosophy and the move toward inclusive educational programming (Paul-Brown & Caperton, 2001). Such models have been used for many years to prepare persons with ID for transitions to independent living and working (Clees, 1996; Luce & Dyer, 1995; Morris, 2002; Patton, Polloway, Smith, & Edgar, 1996; White, Edelman, & Schuyler, 2001; White, Simpson, Gonda, Ravesloot, & Coble, 2010).

    By focusing on multiple everyday contexts, the time available for teaching and the opportunities for learning can be dispersed throughout the day within frequently occurring activities, events, and routines. Intervention in multiple contexts implies a portable approach to service delivery that allows the person with ID to practice functional skills whenever and wherever they are useful and meaningful. It also implies that multiple communication partners besides the SLP are involved in service delivery in various settings.

    ASHA Resources

    Other Resources

    This list of resources is not exhaustive and the inclusion of any specific resource does not imply endorsement from ASHA.

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    Acknowledgments

    Content for ASHA's Practice Portal is developed through a comprehensive process that includes multiple rounds of subject matter expert input and review. ASHA extends its gratitude to the following subject matter experts who were involved in the development of the Intellectual Disability page:

    • Meher H. Banajee, PhD, CCC-SLP
    • Patricia A. Prelock, PhD, CCC-SLP
    • MaryAnn Romski. PhD, CCC-SLP
    • Billy T. Ogletree, PhD, CCC-SLP
    • Krista M. Wilkinson, PhD
    • Howard Goldstein, PhD, CCC-SLP
    • Nancy C. Brady, PhD, CCC-SLP
    • Rose A. Sevcik, PhD
    • Jon F. Miller, PhD, CCC-SLP

    In addition, ASHA thanks the members of the Ad Hoc Committee to Review/Revise Current Practice and Policy Documents Related to Mental Retardation/Developmental Disabilities, whose work was foundational to the development of this content. Members of the Committee were Howard Goldstein (chair), Kevin Cole, Philip S. Dale, Jon F. Miller, Patricia A. Prelock, Krista M. Wilkinson, and Diane Paul (ex officio). Celia Hooper, ASHA vice president for professional practices in speech-language pathology (2003–2005), served as the Board liaison.

    Citing Practice Portal Pages

    The recommended citation for this Practice Portal page is:

    American Speech-Language-Hearing Association. (n.d.). Intellectual Disability. (Practice Portal). Retrieved month, day, year, from www.asha.org/Practice-Portal/Clinical-Topics/Intellectual-Disability/.

    Content Disclaimer: The Practice Portal, ASHA policy documents, and guidelines contain information for use in all settings; however, members must consider all applicable local, state and federal requirements when applying the information in their specific work setting.

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