Mentally retarded children are exceptional children; they belong to the lower end of the scale of intelligence and scholastic aptitude. They are just opposite to gifted and creative children. Some other terminologies are also used for mentally retarded children’s such as, feeble-minded, mentally handicapped, mentally deficient, mentally subnormal, mentally average etc.
Definition of Mentally Retardation
According to Page,
“Mental deficiency is a condition of sub-normal mental development, present at birth or early childhood and characterized mainly by limited intelligence and social inadequacy.”
According to British Mental Deficiency Act,
“Mental retardation is a condition of arrested or incomplete development of mind existing before the age of 18 years whether arising from inherent causes or induced by disease or injury.”
According to American Association on Mental Deficiency,
“Mental retardation refers to significantly sub-average intellectual functioning existing concurrently with deficits in adaptive behaviour and manifested during the development period.”
This definition of American association explains the meaning and nature of mental retardedness in following stages:
Development period: The development period is the period of time between one’s conception and expiry of the period of adolescence, generally the 18th birthday.
General intellectual functioning: This is determined through the results obtained after individual administration of general intelligence tests such as Stanford-Binet intelligence scale or the age-appropriate Wechsler scale.
Significantly sub-average: A significantly sub-average person is that whose full scale I.Q. does not exceed 70 on the Stanford-Binet test. However, student with an I.Q. of 75 or even 79 could be classified as retarded if he demonstrates deficits in adaptive behaviour.
Adaptive behavior: Grossman defined adaptive behavior as “the effectiveness or degree with which the individual meets the standards of personal independence and social responsibility expected of his age and cultural group”. These expectations differ from age to age. However, deficits with regard to these expectations may be manifested by slow, incomplete or arrested development.
Identification of Mentally Retarded
There are few consideration that are kept in mind for the identification of mental retardedness among children:
- Detection or identification must be carried out during the developmental period; i.e. from the embryonic stage to the end of adolescence.
- Behaviour should be closely and objectively observed for detecting defects or deficiencies in adaptive behaviour.
- If adaptive behaviour is judged to be indicative of mental retardedness, it should be confirmed through intelligence test.
- In each case, low I.Q. and deficient adaptive behaviour both should be used as criteria for identifying mental retardedness.
Steps involved in identifying Mental Retardedness
Detection before birth-
Certain tests are used in which a small amount of fluid surrounding the developing foetus is examined, some metabolic diseases, incurable chromosomal abnormalities affecting the developing foetus can be screened at this stage.
Detection at the time of birth-
Soon after the birth many metabolic diseases and developmental defects causing mental retardation may be detected. For example- Phenylketonuria (PKU) can be easily diagnosed in a newborn infant with the help of urine test or blood test. Other diseases like congenital cerebral defects including macrocephaly, microcephaly and hydrocephaly may be detected soon after the birth.
Collecting history of the development of mental retardation-
Proper information about the history of development and causation of mental retardation also helps in the identification of disabilities among the retarded. This information could be in the form of genetic information, prenatal history of the child and the mother’s condition and her experiences during pregnancy, history of labour and delivery, blood group incompatibility, exposure to infections and chronic diseases, intellectual development, emotional episodes, psychological stress etc.
Assessment of intellectual functioning-
Apart from identifying or segregating individuals with subnormal intellectual capacities, I.Q. scores are also used for classifying the severity of their mental retardation into various categories such as moron, imbecile and idiot; or into degrees like moderate, severe and profound. However, merely low I.Q. cannot be used for detection of subnormal intellectual capacity. Following characteristics should also be kept in mind during identification:
- Mentally retarded or subnormal children do not have much power of observation, imagination, thinking and reasoning, and ability to generalize.
- They are not good at abstraction and can only think in terms of concrete objects and situations.
- They take longer time to learn something. Therefore they are slow learners.
- Their general verbal instructions are poor.
- Their rate of intellectual development is very slow in comparison with children of their age.
- The areas of interest, choices and aptitudes are limited.
- Creativity aspect in such children is almost absent.
Assessment in terms of Adaptive Behaviour-
Personality problems and deficiencies in terms of adaptive behaviour may also be assessed through close observation or with the help of tests like adaptive behaviour scale and the Minnesota developmental programming system. Therefore, adaptive behaviour is a helpful criterion in assessment of child’s deficiency.
Causes of Mental Retardation
Numerous factors are believed to cause mental retardation, broadly it is divided into two categories:
- Organic or biological factors
- Socio-psychological factors
Organic or biological factors-
- Genetic factors- Mental deficiency could be caused by genetic factors operative at the time of conception either through transmission of some defective gene or through chromosomal aberration. For example- Phenylketonuria, Klinefelter’s syndrome, Down’s syndrome, Mongolism etc.
- Infection- Many infectious disease like syphilis, rubella, encephatilitis could be a reason for mental retardation in which brain tissue and nervous system can be damaged resulting into mental deficiency.
- Intoxication- Intoxication of various toxic agents like carbon monoxide, mercury, lead and various immunological agents like anti-tetanus serum, rabies, typhoid vaccines etc. may result in brain damage during development after birth.
- Trauma- physical damage to the brain in the form of injuries prior to birth, at the time of delivery or after birth may cause mental retardation.
- Metabolic and endocrine disorders- Disturbance in metabolism may cause mental retardation in which body cells are built and broken down and by which energy is made available for their functioning. Chemical error involving metabolism of fat can cause Tay-Sachs disease whereas disturbed protein metabolism causes PKU.
- Tumours- Brain damage caused due to tumour and other new growths may result into mental retardation.
Psychological factors along with adverse socio-cultural environment leads in causation as well as perpetuation of mental retardation. Children who are denied the satisfaction of their psychological and social needs become over-sensitive to psychological stress.
Prevention of Mental Retardation
Some preventive measures of mental retardation are listed below:
- Tests are there to identify chromosomal anomalies or defective or inferior gene. Genetic counselling should be given to such parents and they should also opt to voluntary birth control.
- Proper care of mother and newborn infant is necessary for preventing mental retardation.
- Normal and stimulating environment should be provided to infant after birth as unfavourable conditions during early childhood may cause mental retardation.
- Provisions of public education should be made. There should be awareness for the right age of having kids. Mental retardation is also caused by toxic agents therefore, public education is important for this aspect as well.
Common Clinical Types of Mental Retardation
The mental deficient whose facial characteristics bear a superficial resemblance to members of the Mongolian race are classifies as mongols. The I.Q. in such individual ranges from approximately 20-25.
They are short statured with small round heads, abnormally short necks, thumbs and fingers, slanting almond-shaped eyes and short flat nose. They usually have a small mouth and fissured & dry lips and tongue. Their hands and feet are broadly clumsy. They have deep voice and don’t have proper motor coordination. They are slow learners.
Mongolism is caused due to faulty heredity or chromosomal anomalies and some metabolic factors. There is no effective treatment or preventive measures for mongolism.
This deficiency is caused as a result of thyroid deficiency. It could range from moderate to severe. The severity of the disease depends upon the age at which the deficiency occurs as well as the degree and duration of the deficiency.
Persons suffering from cretinism have dwarf like, thickset body, coarse and thick skin, short and stubby extremities, wiry consistency hairs in abundance and thick eyelids that give a sleepy appearance.
Early timely treatment is helpful in curing cretinism in which injection of thyroid gland extract is given.
It refers to mental deficiency associated with the failure of cranium to attain normal size due to impaired development of brain. The microcephalic has usually smaller head which rarely exceeds a circumference of 17 inches (whereas normal brain is approximately 22 inches). They are short statured with usual cone shaped skull and receding chin and forehead.
Both genetic and non-genetic factors are responsible for the impair development of brain and thus cause microcephaly. No effective treatment is available for this abnormality.
It is a mental deficiency which results from the accumulation of large amount of cerebrospinal fluid within the cranium, causing damage to the brain and enlargement of the skull. The main symptom of hydrocephaly is the gradual increase in the size of the skull. Causes could be genetic as well as non-genetic. An early diagnosis with proper surgical treatment is found favourable in checking further damage to the brain tissue. But in advanced stage no treatment is helpful and eventually results in death.
This is a genetic disease and is transferred through a recessive gene carrying metabolic disturbance. As a result, at the time of birth, the child lacks an enzyme needed to breakdown phenylalanine (an amino acid found in protein rich foods) which results in abnormal accumulation of phenylalanine in the blood causing damage to the brain tissue.
Symptoms include vomiting, a peculiar musty odour, infantile eczema and seizures, motor incoordination, signs of mental retardation and neurological manifestations relating to severe brain damage. It can be diagnosed by detecting the presence of phenylpyruvic acid in the urine. The success of the treatment of PKU depends on early detection.
This is a rare hereditary disorder of fat metabolism transmitted as a simple recessive characteristic. It is never transmitted directly from patient to offspring because death generally occurs before puberty. The only mode of transmission is through the mating of persons who are the carriers of the defective genes although free from overt symptoms. This disorder occurs in two forms depending upon when it occurs, which are the infantile and juvenile.
The major symptom includes muscular weakness, inability to maintain normal posture, loss of ability to grasp objects, visual difficulties leading to progressive blindness, seizures and neurologic manifestations.
Infantile amaurotic idiocy is also known as Tay-Sachs disease. It occurs in infants, which appears at about 6 months of age and death occurs between the age of two and three years.
Juvenile amaurotic idiocy occurs at 5 or 6 years and the patient may live up to 13 years.
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