Intellectual Disabilities

Intellectual Disability is neither an illness nor a disease. Essentially, the term refers to delayed intellectual growth that is manifested in immature reactions to environmental stimuli and below-average social and academic performance. However, individuals who are described as intellectually disabled vary widely in almost every aspect of human behaviour, personality, and temperament. Students who are intellectually disabled have difficulties with complex academic material; that are markedly slower than their age-mates in reasoning, making judgements, using memory effectively, and any attempts to take into account the incident rate of a relatively common disorder almost invariably fails to take into account some affected individuals. This occurs in the case of intellectual disabilities, where mild conditions prove elusive and are difficult to accurately pinpoint. Many mild cases go unreported, although this is not true in the case of significant intellectual impairments. Different IQ cut-off points are used, different methods of gathering data for prevalence studies are used, different definitions of adaptive behaviour are used, different regions and social classes show different prevalence rates. There are also gender differences within prevalence estimates. Somewhere between 5 and 10 times as many boys than girls are considered to be mildly intellectually disabled. Mild intellectual disability is a particular controversial since children in this category tend to be almost exclusively from poor families often of minority origin. Different age groups also show different prevalence figures. 
There are many other labels in use for children who are considered intellectually disabled. These include developmentally challenged, developmentally disabled, and developmentally delayed. Labels that include the word “developmental” may contribute to the stereotype and false belief that a person with an intellectual disability will never grow up. An intellectual disability does not stop a person from developing, even if the pace, process and outcome of their development may not be considered as “normal” to some. They are unique human beings, growing and changing every day.

Definition of Intellectual Disability: It is not a disease you can catch from anyone and it is not a type of mental illness like depression. There is no ‘cure’ for intellectual disabilities, however most children can find tools and strategies to help them learn; it just may take more time and effort. Disorders such as Downs Syndrome and Autism Spectrum Disorder are intellectual disabilities.

     The AAMR (American Association on Mental Retardation) definition was adopted in 1959 and uses the term mental retardation. Its definition is "mental retardation refers to substantial limitations in personal functioning. It is characterized by significant sub average intellectual functioning, existing concurrently with related limitations in two or more of the following applicable adaptive skills: communication, self-care, home living, social skills, community use, self-discretion, health and safety, functional academics, leisure, and work."


     There are other definitions that prescribe cut-off points to different IQ levels, or suggest that the developmental period ends at a later or earlier age. Despite the differences between various definitions, most of them share three critical points: sub average intellectual functioning, deficits in adaptive behaviour, and manifestation during the developmental period. Sub average general functioning has differed in the IQ score needed to qualify, today it is an IQ score of below 70. At risk, borderline, or slow learners fall between 70-85.  

(Nichy.org)

     Prevelance: Intellectual disabilities are the most common developmental disability: Approximately 6.5 million people in the U.S. alone have some sort of intellectual disability. More than 545,000 between the ages of six and twelve have some level of intellectual disability and receive special education. 1 in every 10 children who need special education has some form of intellectual disability. Approximately 2% of Canadians have been given a diagnosis of intellectual disability. Of these, about 90% have “mild” disabilities. However, labels like “mild” say nothing about the type or intensity of support an individual might require, just as non-disabled individuals in the community have widely varying needs.

           

        An intellectual disability may be congenital (the individual is born with it) or it may be acquired, through accident or disease. Some people associate intellectual disability with specific causation (such as Autism or Down Syndrome,) but in about 50% of cases, the case in unknown and is often described as a “generalized intellectual disability”.
 

     Etiology: Only about half of the cases have a known cause. The most common clinical cause of intellectual disability is Down's Syndrome. The 21st chromosome in these individuals can have disjunction (3 instead of 2), translocation (only part is in triplicate), or mosaicism (faulty distribution of chromosomes in later cell divisions). There is also a fragile X syndrome. Its inheritance pattern is unique. When a male is the carrier, it will be passed only to his daughters. When a female is the carrier, there is a 50% chance of passing it on.
Genetic defects include Williams Syndrome (caused by a deleted chromosome 7, characterised by cardiovascular abnormalities, short stature, and developmental delays), Prader-Willi Syndrome (irregularity with chromosome 15, characterised by obesity, small stature, hands, and feet, mild intellectual disability, learning disabilities, and language disorders),and Angleman Syndrome (deletion of chromosome 15, characterised by severe mental retardation, seizures, ataxia (problems with gait and ambulation), microcephaly, particular facial appearance, and a fascination with water). Infections and intoxicants included rubella, syphilis, paediatric AIDS, and FASD are all instances where a disability can form after birth. In terms of Environmental influences, subtle genetic factors may interweave with socio-economic deprivation to further affect a child's development. Psychosocial disadvantage, poverty, inadequate nutrition, family instability, lack of educational opportunity, or an infant environment that is not stimulating are all referred to as cultural-familial mental retardation.  

Winzer, Margret. "Section 2, Chapter 6." Children with Exceptionalities in Canadian Classrooms. Toronto: Pearson Prentice Hall, 2008. 176, 178, 185, 186. Print.