There Are Five Levels of Intellectual Disabilities

There Are Five Levels of Intellectual Disabilities


Intelligence is the full general mental chapters that involves reasoning, planning, solving problems, thinking abstractly, comprehending complex ideas, learning efficiently, and learning from feel (AAIDD, 2010). Historically, intellectual disability (previously termed “mental retardation”) has been defined by significant cognitive deficits—which has been established through a standardized measure of intelligence, in item, with an IQ score of beneath 70 (ii standard deviations below the mean of 100 in the population)—and also by significant deficits in functional and adaptive skills. Adaptive skills involve the ability to conduct out age-appropriate daily life activities. Two different systems for classifying intellectual disability (ID) used in the United States are that of the American Clan on Intellectual and Developmental Disabilities (AAIDD) and the
Diagnostic and Statistical Transmission of Mental Disorders, 5th Edition
(DSM-5), which is published past the American Psychiatric Clan. Both of these systems allocate severity of ID according to the levels of support needed to achieve an individual’s optimal personal functioning (run into Tabular array 9-1).

Tabular array 9-1

Classifications of Intellectual Disability Severity.

DSM-five defines intellectual disabilities as neurodevelopmental disorders that begin in childhood and are characterized by intellectual difficulties as well as difficulties in conceptual, social, and applied areas of living. The DSM-v diagnosis of ID requires the satisfaction of three criteria:


Deficits in intellectual functioning—“reasoning, problem solving, planning, abstruse thinking, judgment, academic learning, and learning from experience”—confirmed past clinical evaluation and individualized standard IQ testing (APA, 2013, p. 33);


Deficits in adaptive performance that significantly hamper conforming to developmental and sociocultural standards for the private’s independence and ability to encounter their social responsibility; and


The onset of these deficits during childhood.

The DSM-5 definition of ID encourages a more comprehensive view of the individual than was true under the fourth edition, DSM-IV. The DSM-IV definition included impairments of general mental abilities that touch on how a person functions in conceptual, social, and daily life areas. DSM-5 abandoned specific IQ scores as a diagnostic benchmark, although it retained the general notion of performance two or more standard deviations below the general population. DSM-five has placed more accent on adaptive functioning and the performance of usual life skills. In contrast to DSM-Four, which stipulated impairments in two or more skill areas, the DSM-5 criteria point to impairment in one or more superordinate skill domains (e.yard., conceptual, social, practical) (Papazoglou et al., 2014).

Classifications of Severity

The terms “mild,” “moderate,” “severe,” and “profound” have been used to describe the severity of the condition (see Table 9-1). This arroyo has been helpful in that aspects of balmy to moderate ID differ from astringent to profound ID. The DSM-5 retains this grouping with more focus on daily skills than on specific IQ range.

Mild to Moderate Intellectual Disability

The majority of people with ID are classified as having balmy intellectual disabilities. Individuals with balmy ID are slower in all areas of conceptual development and social and daily living skills. These individuals tin can learn practical life skills, which allows them to office in ordinary life with minimal levels of support. Individuals with moderate ID tin can take intendance of themselves, travel to familiar places in their community, and larn basic skills related to prophylactic and health. Their self-care requires moderate support.

Severe Intellectual Disability

Astringent ID manifests as major delays in evolution, and individuals often have the ability to understand speech simply otherwise have limited advice skills (Sattler, 2002). Despite being able to learn elementary daily routines and to engage in simple self-care, individuals with severe ID demand supervision in social settings and often need family care to live in a supervised setting such as a group home.

Profound Intellectual Disability

Persons with profound intellectual disability often have congenital syndromes (Sattler, 2002). These individuals cannot live independently, and they require close supervision and help with cocky-care activities. They accept very limited ability to communicate and often accept physical limitations. Individuals with balmy to moderate disability are less likely to accept associated medical conditions than those with astringent or profound ID.

Evaluation of Severity

Currently AAIDD publishes a framework for evaluating the severity of ID, the Supports Intensity Scale (SIS), which focuses on the types and intensities of supports needed to enable an individual to lead a normal and independent life, rather than defining severity in terms of deficits. The Sister evaluates the support needs of an individual across 49 life activities, divided into half-dozen categories: abode living, community living, life-long learning, employment, health and condom, and social activities.

DSM-5 notes that intellectual performance reflects several dissimilar components: verbal comprehension, working retentivity, perceptual reasoning, quantitative reasoning, abstract thought, and cognitive efficacy (APA, 2013). Authentic measurement requires an instrument that is psychometrically valid, culturally appropriate, and individually administered. In the absence of appropriate measurement instruments, screening instruments are nevertheless able to aid in the identification individuals who need farther testing. IQ test results autumn along the normal (bell-shaped) curve, with an boilerplate IQ of 100, and individuals who are intellectually disabled are usually ii standard deviations below the average (IQ beneath lxx). Various issues (e.g., co-occurring communication problems, sensory or motor difficulties) can affect assessment, and psychologists must accost these in considering which tests to use. IQ scores are unremarkably reported with an associated confidence interval which indicates a range inside which the “true” score is probable to fall.

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A frequently used IQ measure for children in the U.s.a. is the Wechsler Intelligence Calibration for Children (WISC-Five). It historically measured verbal IQ, performance IQ, and full performance IQ (Wechsler et al., 2004). In its most recent edition, the WISC-5 provides an overall IQ score as well as five other scores for verbal comprehension, visual spatial skills, fluid reasoning, working retention, and processing speed (Pearson Education, 2015). Because IQ scores have been constantly rising since the 1930s, standardized IQ tests accept been periodically renormed based on the current population (Flynn, 1987).


Environmental factors such as exposure to toxic substances (eastward.g., prenatal alcohol exposure, prenatal or postnatal lead exposure), nutritional deficiencies (e.g., prenatal iodine deficiency), encephalon radiations, childhood encephalon infections, traumatic brain injury, and maternal infections (east.thousand., rubella, cytomegalovirus) can pb to ID. Additionally, prenatal and postnatal complications—e.g., complications of prematurity such as hypoxemia and periventricular hemorrhage—may cause encephalon injury resulting in ID (Gustafsson, 2003).

Genetic factors play a major role in ID. Different genetic causes may pb to ID. Down’s syndrome (trisomy 21) is the most common genetic crusade of ID in the United states, occurring approximately once every 700 alive births (Parker et al., 2010). Delicate X syndrome is the about common known inherited cause of ID, and it affects approximately one per five,000 males (Coffee et al., 2009). Many cases of ID in the population are of unknown etiology.

Considering of the varied causes and consequences of ID, an initial evaluation should address intellectual and life skills, the identification of genetic and nongenetic etiologies, and the diagnosis of weather that demand treatment (e.m., epilepsy and phenylketonuria). Prenatal and perinatal medical histories, a physical examination, genetic evaluations, and metabolic screening and neuroimaging assessment may aid in the determination of characteristics that may influence the course of the disorder.


ID begins in the first ii decades of life. The age and characteristics of onset depend on the cause of the disability and the severity of the neuropsychiatric dysfunction. The identification of children with more astringent ID (what previously would have been termed astringent and profound mental retardation) typically occurs early in life. These children oftentimes have dysmorphic features and associated medical conditions and higher rates of behavioral and psychiatric disturbances. Individuals with astringent intellectual inability may show delayed motor, linguistic communication, and social accomplishments within the first 2 years of life. Individuals with balmy intellectual disability may not exist recognized until early on school age because that is when their difficulties with academic learning become apparent.

Depending on its cause, ID may be stable and nonprogressive or it may worsen with time. After early on babyhood, the disorder is chronic and usually lasts an individual’s lifetime; notwithstanding, the severity of the disorder may alter with historic period. For example, visual or hearing difficulties, epilepsy, childhood psychological or head trauma, substance abuse, and other medical conditions may touch on the class of the disorder. Conversely, an early intervention may improve adaptive skills.


Males are more likely than females to be diagnosed with ID. Co-ordinate to the National Wellness Interview Survey, from 1997 to 2008 the prevalence of ID was 0.78 pct in boys and 0.63 percent in girls (Boyle et al., 2011). Overall, studies of prevalence show a male backlog in the prevalence of ID, which is partially explained by x-linked causes of the inability, such as fragile X syndrome (Durkin et al., 2007).


In the United States, the prevalence of ID varies past race/ethnicity, probably due to confounding by socioeconomic status (SES). Black non-Hispanic children are approximately twice every bit likely, and Hispanic children approximately 1 and a half times every bit likely, to be diagnosed with ID as white non-Hispanic children (Bhasin et al., 2006; Boyle and Lary, 1996; Boyle et al., 2011; Military camp et al., 1998; Van Naarden Braun et al., 2015). Language differences and poverty likely contribute to the racial and ethnic differences in performance on cognitive tests and to the corresponding disparities in prevalence. Even after taking the effects of SES into account, there is testify that examination bias and diagnostic bias affects the rates of the diagnosis of ID (Jencks and Phillips, 1998).

Socioeconomic Status

Poverty is one of the well-nigh consistent hazard factors for ID (Cooper and Lackus, 1983; Durkin et al., 1998; Stein and Susser, 1963). Boyle and colleagues reported that in the U.s. between 1997 and 2008, the prevalence of ID among children below 200 per centum of the federal poverty level (FPL) was 1.03 percent, while for those above 200 percentage FPL the charge per unit was 0.5 percent (Boyle et al., 2011). Similarly, Camp and colleagues found the prevalence of ID amid children of low SES to exist more than than twice equally high as that amid center- or high-SES children (Camp et al., 1998). The association between depression SES and poverty is considerably stronger for mild than for more severe levels of ID (Drews et al., 1995; Durkin et al., 1998).

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Many neurodevelopmental, psychiatric, and medical disorders co-occur with ID, especially communication disorders, learning disabilities, cognitive palsy, epilepsy, and various genetically transmitted conditions (APA, 2013). Estimates of the rates of psychiatric coexisting conditions vary. For many years at that place was an underestimation of the increased risk for evolution of comorbid conditions (“diagnostic overshadowing”). As research was conducted, it became clear that the risk for comorbid conditions is greater than previously believed. For example, Rutter and colleagues reported rates of xxx to 42 percentage of psychopathology in children with “mental retardation” compared with 6 to 7 percent in children without the disability (Rutter et al., 1970). Gillberg and colleagues reported that 57 percentage of subjects with balmy and astringent “mental retardation” met diagnostic criteria for melancholia, anxiety, deport, schizophrenia, and somatoform disorders and attention deficit hyperactivity disorder (ADHD) (Gillberg et al., 1986). Nearly studies indicate a four- to fivefold increase in mental health issues amongst individuals with ID. In general, at to the lowest degree 25 pct of persons with ID may accept meaning psychiatric problems, with the population experiencing, in particular, significantly increased rates of schizophrenia, depression, and ADHD (Bouras and Holt, 2007; Fletcher et al., 2007).


The diagnosis of ID requires evidence of impairments in real life (adaptive) skills; thus all people with ID demonstrate functional damage. These adaptive abilities chronicle to such things as understanding rules, the ability to navigate the tasks of daily living, and participation in family unit, schoolhouse, and customs activities. Various assessments of such skills are available, such every bit the Vineland Adaptive Beliefs Scales which is a widely used instrument (Sparrow et al., 2005). Cess of these skills helps to programme remediation, i.e., teaching specific skills and working on generalization of skills.


Treatments for ID more often than not autumn into 3 main categories: (1) treatments that accost or mitigate any underlying cause of ID, such as restricting phenylalanine in the diet of patients who have phenylketonuria; (2) treatments of comorbid physical and mental disorders with the aim of improving the patient’s functioning and life skills, such equally targeted pharmacologic treatments of behavioral disorders among children with fragile Ten syndrome (Hagerman and Polussa, 2015); and (3) early behavioral and cognitive interventions, special education, habilitation, and psychosocial supports (Szymanski and Kaplan, 2006).

Guidelines for the assessment and management of ID by and large focus on psychosocial interventions. Challenges vary with the age of the individual and the level of impairment as well as with the presence of other associated conditions (Curry et al., 1997; Moeschler et al., 2006; Shevell et al., 2003; Szymanski and King, 1999). Because individuals with ID tin manifest the full range of psychiatric disorders, medications tin sometimes assistance manage these disorders (Reiss et al., 1982). However, the cognitive and verbal limitations of patients with ID brand the psychiatric diagnostic procedure difficult. These disorders oft reply to standard psychiatric handling, i.east., medication and psychosocial support, although in the main ID makes handling more than complex.


  • Historically, intellectual disability has been defined past pregnant cognitive deficits, typically established by the testing of IQ and adaptive behaviors. There are no laboratory tests for ID; nevertheless, many specific causes and genetic factors for ID can be identified through laboratory tests.

  • Males are more likely than females to be diagnosed with ID. Poverty is a risk factor for ID, especially for mild ID.

  • The functional impairments associated with ID are generally lifelong. Withal, there are functional supports that may enable an individual with ID to function well and participate in society.

  • Equally a diagnostic category, IDs include individuals with a wide range of intellectual functional impairments and difficulties with daily life skills. The levels of severity of intellectual impairment and the need for support can vary from profound to mild.

  • Comorbidities, including behavioral disorders, are common.

  • Handling usually consists of appropriate education and skills preparation, supportive environments to optimize functioning, and the targeted treatment of co-occurring psychiatric disorders.


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There Are Five Levels of Intellectual Disabilities


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