Intellectual Disability - Stucky PDF

13 Intellectual Disability Jennifer L. Huffman Definition As part of a multimethod approach, the identification of intellectual disability (ID), formerly known as mental retardation, involves several aspects: Intellectual functioning is typically measured with individually admin...

13 Intellectual Disability Jennifer L. Huffman Definition As part of a multimethod approach, the identification of intellectual disability (ID), formerly known as mental retardation, involves several aspects: Intellectual functioning is typically measured with individually administered intelligence tests, with an intelligence quotient (IQ) score of approximately two standard deviations below the population mean (65–75) needed to diagnose ID. Individuals with ID also need to show deficits in adaptive functioning relative to expectations for chronological age and sociocultural background in conceptual, social, and practical domains across multiple environments, such as home, school, work, and community. The onset of symptoms occurs during the developmental period, specifically during childhood or adolescence. Severity of ID is defined on the basis of adaptive functioning (not IQ scores) because adaptive functioning determines the level of supports required, and IQ measures are less valid in the tail end of the IQ range. Neuropathology The majority of cases of ID result from changes in early brain development, which can be influenced to some extent by environmental factors. Research is growing regarding neuropathology for specific etiologies of ID.  Changes in early brain development can result in reduced cerebral volume or severe diffuse pathology. In some cases, microcephaly with differential volume reduction in certain regions of the brain is evident (e.g., fetal alcohol syndrome). In other cases (e.g., autism), enlarged head circumference is accompanied by mild ventricular enlargements and/or enlargement of some brain structures. These changes are believed to be related to a disruption of neuronal proliferation, apoptosis, migration, synaptogenesis, and/or dendritic pruning. Epidemiology The overall prevalence of ID globally is estimated to be less than 1%. The bell curve model that predicts 2.5% would have an IQ score of 70 or less does not take into account delayed diagnosis (especially for cases of mild ID) and the association between life expectancy and severity of ID. The ratio of males to females is 1.5:1, in large part due to the number of X- linked syndromes that cause ID (e.g., fragile X syndrome). Causes of ID can be genetic (e.g., Down syndrome, fragile X syndrome, Williams syndrome, Tay-Sachs disease, maple syrup urine disease, Prader- Willi syndrome, Angelman syndrome, Klinefelter syndrome, tuberous sclerosis) or acquired (e.g., prematurity/low birth weight, exposure to alcohol and other drugs, environmental toxins, traumatic brain injury, infections, iodine deficiency, stroke, epilepsy, meningitis, whooping cough, anoxia). The remaining cases are idiopathic or of unknown cause. Down syndrome is the most prevalent form of ID with a known genetic etiology. Fragile X syndrome is the most common familial or inherited form of ID with a known genetic etiology (see Chapter 18, Chromosomal and Genetic Syndromes, for more detail). The leading worldwide preventable cause of ID is iodine deficiency causing thyroid hormone deficiency during pregnancy. Another common environmental and preventable cause of ID is fetal alcohol syndrome.  Current guidelines recommend chromosome microarray as a first-line test for children with ID of an unknown cause, which replaces the standard karyotype and fluorescent in situ hybridization (FISH) tests. Other important tests include fragile X testing, testing for inborn errors of metabolism, and brain MRI in certain children. Establishing an etiologic diagnosis confers certain benefits, such as: clarifying etiology, understanding prognosis or expected clinical course, discussing genetic recurrence risks, identifying potential complications, and providing condition specific family support. Morbidity depends on the severity of ID, as well as comorbid diagnoses.  Approximately 85% of individuals with ID are classified in the mild range. Individuals with mild ID show delays in language but are usually fluent speakers in adolescence. They may acquire academic skills up to the sixth-grade level. They are immature in social interactions, with more concrete language and problem-solving skills compared to same-age peers. They may function appropriately with personal care but need some support with complex daily living skills relative to peers. Competitive employment is often attained in jobs that do not emphasize conceptual skills. They often require support for making healthcare/legal decisions and raising a family. Approximately 10% are classified as moderate ID. They normally attain functional language by adolescence, acquire academic skills up to the second-grade level, and require moderate levels of supervision. They demonstrate a capacity for establishing meaningful relationships with family and friends but have difficulty accurately perceiving social cues, with limited social judgment and decision-making skills. With extensive teaching, they can care for basic personal needs and participate in household tasks (reminders may be needed). Independent employment in jobs requiring limited conceptual and communication skills is possible, with considerable support needed to manage certain aspects, such as social expectations, scheduling, and financial management. Development of recreational skills requires additional supports and learning over an extended period of time. Maladaptive behavior (present in a significant minority) can cause social problems. About 3–4% show severe ID and display limited language (e.g., single words or phrases and use of gestural communication), demonstrate poor academic-related skills (e.g., may demonstrate familiarity with the alphabet and simple counting), and require extensive supervision. They depend on family members and familiar others for pleasure and help. They cannot make responsible decisions regarding well-being of self or others. Work and recreation skills require ongoing supervision and support. Maladaptive behavior (present in a significant minority) can include self-injury. The remaining 1–2% exhibit profound ID and may learn single words, acquire no academic skills, and require pervasive supervision and  support for all activities. Conceptual skills generally involve using physical objects in a goal-directed manner. They may understand simple instructions or gestures and express themselves primarily through nonverbal, non-symbolic communication. They enjoy relationships with well-known family members or familiar others. They might be able to participate in some activities of daily living. Simple actions with objects form the basis of vocational activities. Comorbid physical and sensory impairments may prevent functional use of objects and participation in many social, home, recreational, and vocational activities. Maladaptive behavior is present in a significant minority. Persons with limited intellectual development learn more slowly than persons with typical intellectual development, making it difficult for them to acquire new information and learn skills important for independent living. The majority of individuals with ID reside with family members, although others reside in group homes or live semi-independently with some supervision. Individuals with mild ID often work successfully in supported employment settings, with some success being reported for the other three types of ID as well. Research suggests that persons with different forms of ID differ behaviorally (e.g., boys with fragile X syndrome and Down syndrome). Furthermore, behavioral differences can be found depending on the type of transmission. For example, Angelman syndrome results from a deletion on chromosome 15 contributed by the mother, whereas Prader-Willi syndrome results from a deletion on the same chromosome contributed by the father or by receiving two chromosome 15’s contributed by the mother (maternal uniparental disomy). Angelman syndrome involves ID, sleep disturbance, seizures, jerky movements, frequent laughter or smiling, and usually a happy demeanor. In contrast, Prader-Willi syndrome involves low muscle tone, short stature, incomplete sexual development, ID, compulsive behaviors, and chronic feelings of hunger that lead to excessive eating. Moreover, individuals with Prader-Willi syndrome caused by the deletion show greater maladaptive behaviors and cognitive impairment than individuals with Prader-Willi syndrome caused by uniparental disomy. Certain personality characteristics associated with particular syndromes might affect morbidity. For example, an outgoing nature might predict increased vulnerability to being taken advantage of by others, and mood disturbance could impact the ability to live or work with others. Individuals with ID have a shorter life expectancy (in the 60s) than individuals without ID (in the 70s). Although life expectancy has improved overall in recent years, a good deal of variability is apparent depending on the cause and severity of the ID. For example, the life expectancy for individuals with Tay-Sachs disease is 4 or 5 years, and the life expectancy for individuals with Down syndrome is 60 years. Determinants of Severity By definition, an ID diagnosis requires a combination of an individually administered intelligence test and a formal measure of adaptive functioning. Deficits in intellectual functions such as reasoning, problem solving, planning, abstract thinking, judgment, academic skills, and learning from experience need to be confirmed by both clinical assessment and individualized, standardized intelligence testing. Current diagnostic guidelines emphasize the importance of assessing adaptive functioning and relying on this information to specify the severity of ID. Deficits in adaptive skills limit functioning in one or more activities of daily living, such as competence in language, memory, academic skills, practical knowledge, judgment in novel situations, social communication skills, social judgment, friendships, personal care, job responsibilities, financial management, self- management of behavior, recreation, and work. Scales administered early in development were not designed as measures of intelligence, and research suggests they are most predictive of subsequent identification of ID for children who score lowest in the developmental quotient range. Commonly used measures of developmental functioning include the Bayley Scales of Infant Development and the Mullen Scales of Early Learning. Frequently used measures of intellectual functioning include the Wechsler series intelligence tests, the Differential Abilities Scales, the Kaufman series intelligence tests, the Stanford-Binet Intelligence Scales, and the Leiter International Performance Scales. Interpretation of scores on these measures needs to take into account the standard error of measurement for a given test because scores falling at the border could reasonably be categorized as ID depending on adaptive functioning level. See Chapter 8, Psychometrics, Test Design, and Essential Statistics, and Chapter 9, Test Administration, Interpretation, and Issues in Assessment, regarding psychometric issues in general and confidence intervals in particular. Commonly used measures of adaptive functioning include the Vineland Scales of Adaptive Behavior, Adaptive Behavior Assessment System (ABAS), and Scales of Independent Behavior (SIB). These measures are questionnaires or interviews administered to family members, caregivers, or teachers who know the individual well. Commonly evaluated adaptive skills include conceptual skills (e.g., competence in memory, language, basic academic skills, problem-solving, judgment in novel situations), social skills (e.g., awareness of the thoughts and feelings of others, empathy, interpersonal communication skills, peer relationships, social judgment), and practical skills (e.g., personal care, job responsibilities, financial management, recreation, self-management of behavior). Adaptive measures also may include ratings of fine and gross motor functioning. It is critical to include multiple measures of adaptive functioning from multiple sources, and interpret scores from standardized measures and information gathered from interviews with clinical judgment given the potential for bias and the importance of these measures in determining severity of ID. Presentation, Disease Course, and Recovery The first indicators of ID often include failure to meet developmental milestones and/or physical characteristics associated with certain conditions that cause ID (e.g., facial features in Down syndrome, growth deficiency and/or craniofacial abnormalities in fetal alcohol syndrome). Individuals with ID often exhibit simple, concrete play. Behavioral outbursts and temper tantrums early on are common. In less affected individuals, indications may not be apparent until they enter school and fail to meet educational expectations for their age, particularly on tasks requiring abstract reasoning, retention, and generalization of information. Individuals with ID often exhibit motor and language developmental delays, have a hard time remembering information, struggle to understand social rules, have difficulty understanding the consequences of their actions, and have difficulty solving problems. Their skill development tends to level out in early adolescence, with growing gaps between them and normally developing peers once expectations for abstract thinking and problem- solving increase. In the United States, early intervention services are provided by each state from birth to 3 years of age. Individuals with ID are eligible to receive special education services under federal law from ages 3 to 21. In Canada, similar services are provided but vary by province. Mainstreaming for children with mild ID is the preferred option by many parents and educators and has the advantage of exposing individuals with ID to children with normally developing social and emotional skills. However, individualized attention may be more limited in a mainstream setting. Children with more severe disability are often placed in self-contained classrooms or attend schools for students with special needs in order to receive appropriate support for their multiple needs. Children with ID require special accommodations and modifications to their curriculum for optimal learning such as: having tasks broken down into small component steps to be learned in sequence. hands-on, concrete approaches and visual materials when being taught. immediate feedback regarding performance. As children reach junior high school, emphasis typically shifts from acquiring academic skills to acquiring functional skills, such as learning how to count money, management of personal hygiene, learning social communication/norms, and low-skill job preparation. In some states, students with a diagnosed ID are eligible to receive support services through the educational system for longer than federal law requirements. However, after age 21, individuals with ID are typically serviced through the state departments of developmental disabilities.  Because it is most often not possible to normalize the core cognitive deficits in ID, interventions focus on prevention and improving quality of life. Prevention efforts for reducing the incidence of ID include: Education regarding proper nutrition and eliminating alcohol and drug use during pregnancy Childhood helmet utilization Childhood vaccinations Screening of medical and genetic conditions that are known to cause ID if not treated early (e.g., phenylketonuria, hypothyroidism) Agencies around the world provide assistance for individuals with ID through the development of individual service plans. Such plans are developed following an assessment of individual needs and competencies to optimize the functioning and life satisfaction of the individual with ID. Interventions are recommended to improve social and independent living skills and create a match between the environment and abilities of the individuals being assessed. Applied behavior analysis (ABA) is an evidence-based intervention program used to treat problem behaviors in ID. Individuals with ID are often placed in supported employment situations with a goal of helping them reach the least restrictive level of supervision and support. Medical intervention and medication treatment are used to address comorbid conditions. Recovery is not expected in individuals with ID. Stable performance on IQ and adaptive functioning measures is expected over time, with some exceptions. Depending on the underlying etiology of ID, certain individuals are at increased risk for problems as they age. For example, evidence suggests that individuals with Down syndrome and fragile X syndrome show declining IQ scores into adulthood. Additionally, individuals with Down syndrome are prone to developing Alzheimer disease and tend to die within 8 years of this diagnosis. Associated illnesses, such as heart disease or diabetes, are common in certain conditions (e.g., Williams syndrome, Down syndrome) and require special treatment considerations to prevent premature death. Expectations for Neuropsychological Assessment Results Historically, ID has been thought to affect cognition in a global way, with general slowing in development. However, recent evidence suggests that specific cognitive and behavioral profiles occur across various ID conditions.  Intelligence/Achievement Performance on intelligence tests usually measures at 70 or below, although it is sometimes as high as 75. Declining scores are expected for certain causes of ID (e.g., Down syndrome, fragile X syndrome). In certain conditions, relative differences in verbal and nonverbal abilities are expected such as in autism (verbal worse than nonverbal) or Williams syndrome (verbal better than nonverbal). Performance on measures of academic achievement vary, with some individuals with ID performing quite well on rote measures such as word recognition, spelling, and solving simple mathematics problems. These individuals often perform much more poorly on higher level academic tasks such as reading comprehension, written production, mathematics reasoning, and other similar tasks that involve increased inferential reasoning and problem- solving. Attention Problems with attention are common in individuals with ID. Research suggests that the prevalence of attention problems varies according to the etiology of the ID. In other words, some individuals with ID exhibit worse attention deficits than would be predicted by intellectual level alone. Proper diagnosis and treatment of attention disorders is important in treating individuals with ID because these comorbid problems often go untreated. Processing Speed Slowed processing speed and extra time needed to process cognitive information is a common problem for individuals with ID. Language Language functioning varies by severity and cause of ID, as well as by environmental influences. For example, individuals with Williams syndrome often show relative strengths in language tasks compared to their visuospatial skills. One-word receptive language skills are often a relative strength in individuals with ID who have received extensive language support through early intervention or an enriched home environment. Visuospatial Visuospatial problems are often found in individuals with ID and vary by etiology. For example, spatial cognition is below mental age expectations for individuals with Williams syndrome yet is often a relative strength for individuals with autism or Down syndrome.  Memory Evidence of different profiles of memory difficulties for different causes of ID are emerging from the literature, including differences in verbal and spatial immediate memory and short-term memory among groups that do not fully correspond to general differences in cognitive functioning. In general, individuals with ID exhibit weaknesses with long-term memory. Executive Functions Executive functions are generally impaired in individuals with ID, and a growing body of research is attempting to explore the specific executive functioning differences for individuals with ID. For example, some individuals with ID have good working memory skills yet poor pragmatic judgment and trouble-shooting abilities. Some have shown deficits with sequential processing or inhibitory control. Others show specific problems with updating working memory. Yet others display behavioral problems associated with attention disorders such as inattention, hyperactivity, impulsivity, and transition problems. Sensorimotor Functions Significant delays in the development of all sensorimotor skills is expected in individuals with ID. Emotion and Personality Individuals with ID often exhibit problems with impulse control, frustration tolerance, behavioral regulation, mood, and low self-esteem that vary with diagnosis type and age. For example, children with fetal alcohol syndrome often exhibit increasing behavioral problems during puberty. Specific syndromes have certain associated personality characteristics, such as the outgoing nature and associated fears and anxieties in children with Williams syndrome. Additionally, young children with Prader-Willi syndrome are described as friendly and affectionate but the onset of hyperphagia is associated with increased temper tantrums, stubbornness, impulsivity, food stealing, and compulsive behaviors. Symptom and Performance Validity Assessment of test engagement is important in individuals with ID, although research suggests that a cautious approach is needed when using common measures of performance validity. Considered in isolation, performance validity tests (PVTs) might result in misclassification of individuals with ID as providing noncredible effort, given the possibility of false-positive  errors. At the same time, well-motivated individuals with IQs in the mild ID range rarely fail PVTs that have been demonstrated to have high specificity. In choosing PVTs for an individual with ID, consideration needs to be given to the specific task demands of the test, as well as the individual’s areas of cognitive deficit, reading level, behavioral problems, neurological disease, and age. For individuals with ID, more stringent cutoff scores (to maintain at least 90% specificity) might be needed on some PVTs and alternate administration might be required (e.g., a combined oral-computer administration with the examiner operating the mouse, trackpad, or keys). When possible, consider the use of PVTs specifically designed for individuals with ID. Sensitivity and specificity for determining poor validity is maximized by failure on two or three PVTs using appropriate adjusted cutoffs. Keep in mind that below-chance performance is still indicative of malingering, and research suggests that approximately 10% to 13% of low-IQ individuals seeking disability benefits obtain significantly below-chance performance. Carefully considering developmental history and utilizing multiple PVTs, qualitative analysis of response errors, and observations of behavioral inconsistencies are crucial when evaluating the validity of results for individuals with ID. Considerations when Treating Patients with ID  Driving Research indicates that individuals with mild ID are capable of learning the skills necessary to drive, particularly if their driving is limited to short distances and familiar routes. However, few programs provide needed assistance with obtaining a license. Work As noted, individuals with mild ID are often successful in supported work settings. School and Vocational Training Individuals with ID qualify for educational programming from age 3 to 21 under United States federal law; additional services before and after these ages may be provided, but the duration varies by state. Individual service plans are developed based on needs and competencies with a goal of utilizing competencies while addressing needs to optimize functioning. Individuals with mild ID are often successful in vocational training programs with supervision and support. Capacity Assessment of the decision-making capacity for individuals with mild ID requires careful consideration of the specific capacity in question, along with relevant laws. Psychological and Emotional Issues Individuals with ID are about four or five times more likely to be diagnosed with a psychiatric disorder than normally developing peers. Thus, assessment and treatment for comorbid psychiatric disorders is important. Severe Psychiatric Complications Individuals with severe psychiatric complications are at increased risk for behavioral problems and need for extensive supervision. Psychiatric treatment and specialized group home placement are often required. Medications Medication management is recommended to treat comorbid problems with ID, including problems with attention, underlying seizures, diabetes, heart disease, and mood disorders. Supervision to ensure proper administration of medications is often needed. Risk Factor Modification Primary prevention of ID includes improving the nutritional status of women of child-bearing age (e.g., folic acid and iodine supplementation), immunizations prior to pregnancy, avoiding exposure to harmful chemicals during pregnancy  (e.g., alcohol, nicotine, or illicit drugs), education regarding increased risk of complications in pregnancy with advancing maternal age, detection and care for high-risk pregnancies, maternal screening and treatment (e.g., syphilis, Rh incompatibility), provision of high-quality neonatal intensive care services, reduction of environmental pollutants (e.g., lead), immunization of children, and genetic counseling. Advances in prenatal screening and diagnosis also offer preventative options but carry ethical implications. Secondary prevention includes neonatal screening and appropriate medical treatment (e.g., phenylketonuria, galactosemia, hypothyroidism) and intensive early intervention services for children at risk for developing ID. Tertiary prevention includes appropriate education, training, and support for families and caregivers. Interpersonal Relationships Individuals with ID are often capable of establishing interpersonal relationships with peers of a similar mental age. As they age, keeping up with rapid-paced conversation becomes increasingly difficult, given slowed processing speed and communication limitations. Many individuals with ID form intimate relationships, although they are also generally at risk for being exploited, including sexually. Practical Issues Care needs to be taken as individuals with ID transition from pediatricians to adult-oriented healthcare providers, who may be ill-prepared to treat their associated medical and mental health conditions. Because individuals with ID often live with their aging parents, parents should be advised to set up caregiving arrangements in the event of their incapacity. Such a transition should be made prior to the event of their incapacity to prevent an adult child with ID from coping with a major transition and the incapacity of their parents at the same time. Rehabilitation Considerations An individualized approach should be taken when developing a treatment program for individuals with ID because many individual differences influence appropriate programming. Providers need to fully understand the patient’s premorbid level of functioning by conducting a careful review of available records. Providers also need to pay special attention to any  behavioral needs that can be addressed through a formal behavioral modification system in addition to necessary rehabilitation services. Cultural Issues Caution is needed when testing individuals from minority groups, given controversy with possible test bias. Sensitivity to cultural and language issues and use of a multimethod approach is recommended. Relevant Definitions Adaptive functioning Abilities in the areas of communication, self-care, home living, social skills, community use, self-direction, health and safety, functional academics, leisure, and work. Applied behavior analysis (ABA) A highly structured behavioral treatment with empirical support for treating problem behaviors in individuals with ID. Mild ID Approximately 85% of individuals with ID score in the mild range. Such individuals show delays in language but are usually fluent speakers in adolescence. They may acquire academic skills up to the sixth- grade level. They often require intermittent supervision and guidance. Moderate ID Approximately 10% of individuals with ID score in the moderate range. Such individuals normally attain functional language by adolescence, acquire academic skills up to the second-grade level, and require moderate levels of supervision. Profound ID Approximately 1–2% of individuals with ID score in the profound range. Such individuals may learn single words, acquire no academic skills, and require extensive supervision. They are dependent on others for physical care. Severe ID Approximately 3–4% of individuals with ID score in the severe range. Such individuals display limited language, may demonstrate familiarity with the alphabet and simple counting, and require extensive supervision. Intellectual Disability Questions NOTE: Questions 19, 78, and 112 on the First Full-Length Practice Examination, Questions 22 and 56 on the Second Full-Length Practice Examination, Questions 25, 94, and 109 on the Third Full-Length Practice Examination, and Questions 31, 71, 88, and 122 on the Fourth Full-Length Practice Examination are from this chapter.