Intellectual disability: New name for an old problem???

It is never easy for any one to deal with a child with mental retardation. It is hard for the child no doubt, but equally hard for the parent to come to terms with the fact, and harder still for the dentist to approach the subject with the parent. 

A blunt " Is your child normal?" is not only insulting to the parent and child alike but also; given the broad range of the term "normal" thoroughly unprofessional. 

One of the ways in which the profession has tried to circumvent this problem has been to come up with newer and more "socially correct" terms. But does this really help us understand the condition or does it simply complicate matters by presenting us with a confusing array of terms which mean little to most? In this series of posts DCSN takes a look at our understanding of intelligence, intellect and the various conditions which manifest with intellectual disability.

Definition

The evolution of the term

Intelligence and measuring intelligence

Conditions which manifest with intellectual disabilty

Intellectual disability: The Evolution of the term

As late as the an first two decades of this century people with mental disorders were routinely referred to by terms that would seem shocking today; the picture above is taken from a leading book on ,mental health in children published in 1913. Fortunately today such degrading terms are no longer acceptable to society. However we remain in just as much confusion over how to address the person with intellectual disability. Over the years different authors and associations have tried to define a set of terms. Here we look at those terms and the rationale for adopting the term intellectual disability.

The story of how we treat individuals with intellectual disability can be traced by studying the evolution of the institutions we have set up to treat, study and better the lives of individuals with intellectual disability. From the punitive ,methods of the 19th century where people were branded as lunatics and chained, to the 21st century we have indeed come a long way. One of the organizations that has played an important and certainly influential role in how we perceive impaired intellect has been the American association on intellectual and developmental disabilities (AAIDR) previously called the American Association on Mental Retardation (AAMR).

Founded in 1876, AAIDD is the world's oldest and largest interdisciplinary organization of professionals concerned about mental retardation and related developmental disabilities. With headquarters in Washington, DC, AAIDD has a constituency of more than 50,000 people and an active core membership of over 3,500 in the United States and in 55 other countries. The mission of AAIDD is to promote progressive policies, sound research, effective practices, and universal rights for people with intellectual disabilities.

AAIDD has updated the definition of mental retardation ten times since 1908, based on new information, changes in clinical practice, or breakthroughs in scientific research. The 10th edition of Mental Retardation: Definition, Classification, and Systems of Supports (2002) contains a comprehensive update to the landmark 1992 definition and provides important new information, tools, and strategies for the field and for anyone concerned about people with intellectual disability.AAIDD anticipates publishing the next classification manual in 2010/2011.

Intellectual disability is the currently preferred term for the disability historically referred to as mental retardation. Although the preferred name is intellectual disability, the authoritative definition and assumptions promulgated by the American Association on Intellectual and Developmental Disabilities (AAIDD and previously, AAMR) remain the same as those found in the Mental Retardation: Definition, Classification and Systems of Supports manual 

What is Intellectual disability?

Intellectual disability is a disability characterized by significant limitations both in intellectual functioning and in adaptive behavior as expressed in conceptual, social, and practical adaptive skills. This disability originates before the age of 18.

The term intellectual disability covers the same population of individuals who were diagnosed previously with mental retardation in number, kind, level, type, and duration of the disability and the need of people with this disability for individualized services and supports. Furthermore, every individual who is or was eligible for a diagnosis of mental retardation is eligible for a diagnosis of intellectual disability.

What causes intellectual disability?

Intellectual Disability or mental retardation is an umbrella term which is seen in a wide variety of conditions. Strictly speaking the clinician should treat intellectual disability as clinical sign suggestive of an underlying pathology rather than as a disease in itself. Given below is a list of conditions that can lead to intellectual disability

Causes of intellectual disability

(from Bherman Et al (ed) Nelson's Textbook of Pediatrics)

Category	Type	Examples
Prenatal (causes before birth)	Chromosomal disorders	Downs syndrome*, Fragile X syndrome, Prader Wili syndrome, Klinefelters syndrome
	Single gene disorders	Inborn errors of metabolism, such asgalactosemia*, phenylketonuria*,mucopolysaccaridoses Hypothyroidism*, Tay- Sachs disease        Neuro-cutaneous syndromes such as tuberous     sclerosis, andneurofibromatosis Brain malformations such as geneticmicrocephaly, hydrocephalus and  myelo-meningocele* Other dysmorphic syndromes, such as Laurence  Moon Biedl syndrome
	Other conditions of genetic origin	Rubistein Tabi syndrome De Lange syndrome
	Adverse material / environmental influences	Deficiencies* , such as iodine deficiency and folic acid deficiency Severe malnutrition* in pregnancy Using substances * such as alcohol (maternal alcohol syndrome), nicotine, and cocaine during early pregnancy Exposure* to other harmful chemicals such as  pollutants, heavy metals,abortifacients, and harmful medications such as thalidomide,phenytoin and warfarin sodium in early pregnancy Maternal infections such as rubella*,syphillis*,    toxoplasmosis,cytomegalovirus and HIV       Others such as excessive exposure to radiation*, and Rh incompatibility*
Perinatal  (around the time of birth)	Third trimester ( late pregnancy)	Complications of pregnancy* Diseases* in mother such as heart and kidney  disease and diabetes Placental dysfunction
	Labour (during delivery)	Severe prematurity, very low birth weight, birth  asphyxia Difficult and/or complicated delivery*  Birth trauma*
	Neonatal (first four weeks of life)	Septicemia, severe jaundice*, hypoglycemia
Postnatal  (in infancy and childhood)		Brain infections such as tuberculosis, Japanese  encephalitis, and bacterial meningitis Head injury* Chronic lead exposure* Severe and prolonged malnutrition* Gross understimulation*

Intelligence Testing - IQ and the feasabilty of IQ testing

 Sir Francis Galton   Alfred Binet

The science of testing an individual's intelligence has always been one mired in controversy. From questions about the accuracy of these tests to questions about their ethics; the task of evluating intelligence has always been treated with some measure of skepticism.The history of IQ began in the ninetheenth century with sir Francis Galton. He was a british scientist known as a dabbler in many different fields, including biology and early forms of psychology. After the shake-up from the 1859 publishing of Charles Darwin's "The Origin of Species", Galton spent the majority of his time trying to discover the relationship between heredity and human ability. He believed that mental traits are based on physical factors.

    Galton's ideas on intelligence were influenced also by the work of a Belgian statistician named Lambert Adolphe Jacques Quetelet. Quetelet was the first to apply statistical methods to the study of human characteristics, and actually discovered the concept of normal distribution. However Galton's irrational belief in races with "superior" intellect led to the development of biased and often blatantly unfair tests.

                 It was a Frenchman named Alfred Binet who in 1904 developed the first objective 

intelligence test. Commissioned by the French government to come up with a test to differentiate between children who had an inferior intellect and those who were normal.Binet's test simply put evaluated the average tasks that should be performed by a child of a given age to obtain mental age. This was then divided by the chronological age and multiplied by 100 to get the IQ. This simple formula to date remains the backbone of intelligence testing. Binet's work was brought to America and modified at Stanford University  by Lewis M. Terman , and thus the famous "Stanford-Binet" intellegence test was born. The fourth edition of this test the SB-IV is still widely used.

Left:The orignal Binet test

Obviously the IQ test would require the child to read the questions or at least have the questions read to him/her. A large number of children who have never been to school or who are illiterate  therefore cannot be evaluated by the Binet tests. In order to overcome this difficulty the Wechsler Intelligence tests were developed. The Wechsler Intelligence Scale for Children (WISC), developed by David Wechsler, is an intelligence test for children between the ages of 6 and 16 inclusive that can be completed without reading or writing.The WISC was originally developed as a downward extension of the Wechsler Adult Intelligence Scale in 1949. A revised edition (WISC-R) in 1974 as the WISC-R, and the third edition, the WISC-III in 1991. The current version, the WISC-IV, was produced in 2003.

 While there is no doubt that the testing of IQ can help detect early signs of intellectual disability their accuracy in judging how smart a child is remains questionable. The tests also have an element of bias. All tests retain an element of cultural knowledge. An Indian child may not know what a snowman is or what blueberry pie tastes like, not because he/she is dull, but for the obvious reason that he/she has very little chance of having seen either. It is for this reason that several IQ tests have been developed specifically keeping in mind the Indian population.

The Standford-Binet test has been adapted for an Indian population by Kamath in 1940 and is known as the Binet-Kamath Test. One of the critisisms of this test however has been that the test provides tasks that are too easy and therefore do not accurately measure IQ. The Bhatia IQ test is another widely used IQ test for Indian children Most intelligence tests are designed to provide an I.Q. (intelligence quotient) score. The mental age is based on a set of norms that have been devised by collecting data on a fairly large sample of children of different ages, whom the test makers believe are representative of a population at large.

 One of the criticisms of I.Q. tests is that most tests are not truly representative, especially regarding lower income and minotiry groups. Even if I.Q. tests are truly representative, they have some drawbacks. Foremost, traditional psychometric tests of intelligence are based on the proposition that human beings are endowed with a single, "general faculty" for acquiring information. Secondly, as a person is given a fixed I.Q. score, his/her intelligence is taken to be a fixed, unchanging entity. Traditional tests of intelligence do not take situational and contextual information into account. Thirdly, they penalise a child for a creative or unconventional answer.

In conclusion we can say that the testing of intelligence is only a tool for the diagnosis of intellectual disability. Using these tests to evaluate the brilliance of the child is not only unfair, but also most probably inaccurate.