Mental Retardation, mental deficiency, mental, deficiency, mental sub normality, and mental handicap are some of the terms used to refer to the same condition. The terms used in the past such as idiocy, feeble minded, moron, imbecile and oligophrenia are now no longer used.
Definition
Most comprehensive definition given by the American Association on Mental Retardation (AAMR) in 1983
“Mental Retardation Refers to significantly sub average general intellectual functioning resulting in or associated with concurrent impairments in adaptive behaviour and manifested in the developmental period.”
The points to note:
* General Intellectual functioning is defined as the results obtained by the administration of standardized general intelligence tests developed for the purpose and adapted to the conditions of the country or region.
* Significantly sub average – is defined as IQ of 70 or below on standardized measures of intelligence. The upper limit is intended as a guideline; it could be extended to 75 or more depending on the reliability of the tests used.
* Adaptive Behaviour is defined as the extent to which the individual meets the standards of personal independence and social responsibility expected of his age and cultural group. The expectations of adaptive behaviour vary with the chronological age. The deficits in adaptive behaviour may be reflected in the following areas:
During infancy and early childhood
1. Sensory and motor skill devt
2. Communication skills including speech and language
3. Self help skills
4. Socialization
During childhood an adolescence
1. Application of basic academic skills to daily life activities
2. Application of appropriate reasoning and judgment in the mastery of the environment
3. Social skills
During late adolescence and adult life
1. Vocational and social responsibilities and performance
* Developmental age is defined as the period between conception and 18 years
CLASSIFICATION
Objectives of classification are:
1. Assistance in the use of an acceptable uniform system
2. Helping in diagnostic, therapeutic and research purposes
3. Facilitating efforts at prevention
4. Helping to identify children for services – govt aid etc
Classification Schemes
o Educational
1. Educable
2. Trainable
3. Custodial
o Psychological
1. Mild – IQ 50 -70
2. Moderate IQ 35 -49
3. Severe IQ 20 -34
4. Profound IQ below 20
The various classifications provide an understanding of the level at which the MR person functions with respect to his education, appropriate beh and degree of independence. The characteristics of MR persons vary depending on the level of retardation. However many MR persons may not fit exactly the given description. There may be overlap in certain cases.Before we label a person as MR, esp. in the mild category we have to consider certain factors. Members belonging to low socio economic groups and certain cultures may score low on standardized tests of intelligence and thus may be termed as MR. However they will be functioning within normal limits acc to their cultures criteria.
PREVELENCE
It is generally considered that 2% of the population constitutes persons with MR. However there is no systematic census to determine the prevalence of MR in India. Recently it has been estimated that in India there are about 20 million persons who are mildly retarded and about 4 million who are moderately and severely retarded
CAUSES OF MENTAL RETARDATION
Prenatal Causes
1. Chromosomal Disorders
There are 46 chromosomes in each human cell. 23 from each parent. Errors in chromosomes produce conditions with medical problems and most of these conditions cause MR. The error may be in the number of chromosomes – too many or too few or it may be in the structure of the chromosome.
One common condition due to error in the chromosomes number is Downs Syndrome or Trisomy 21 where there is an extra chromosome at No 21. It was discovered by L Down in 1866 and accounts for 10% of MR cases. This syndrome has some striking physical features such as flat appearance of face, slanting eyes, small ears, protruding and thick tongue, short limbs, short fingers, single crease on hand, respiratory and visual problems.
2. Genetic Disorders
Defect in genes transmitted from parent to offspring can result in certain conditions with MR. The parent may not have the defect or even if they do they may not manifest the condition. A number of genetic disorders are recognized. In some there is a metabolic abnormality and a specific enzyme may be deficient or absent. One such disorder is PHENYLKETUNORIA or PKU
o Caused by the imbalance of amino acids > poor metabolism
o Signs – musty odour, vomiting, hyperactivity, behaviour disorders
o Light skin, blond hair, microcephaly
o Treated by medicines and diet
Brain Damage
o From infections
o Before or after birth
o Rubella, syphilis, herpes simplex
o Meningitis
o Encephalitis
o AIDS
Maternal Diseases
o Diabetes
o High blood pressure
o Chronic kidney problems
o Hypothyroidism – cretinism
o Hyperthyroidism – defects in the CNS leading to MR
From the environment
o Injury
o Poisons
o Radiation
o Malnutrition
o Alcohol or drug abuse
Congenital defects of the central nervous system such as hydrocephalus, microcephaly and a no of defects of the brain and spinal cord are associates with MR
Perinatal Causes
* Premature birth – between 28 and 34 weeks
* Low birth weight (less than 2 kgs)
* Lack of respiration immediately after birth (the brain suffers irreversible damage if it is deprived of oxygen for 4 to 5 min)
* Trauma to the brain due to factors such as excessive moulding due to disproportion between the foetal head and birth canal or prolonged labour or
delivery by improper use of instruments – forceps deliveries
* Excessive coiling of the umbilical cord around the neck of the foetus
* Mothers age – under 20 or above 40
* Closely spaced pregnancies
* History of miscarriages
* Blood incompatibility – the RH factor
* Abnormal position of the foetus in the uterus
* Abnormal position of the placenta
* Toxemia
* Severe jaundice I the new born
* Medicines administered to the mother during preg
Postnatal Causes
* Malnutrition in the child
* Infections such as meningitis, encephalitis
* Epilepsy
* Injury to the brain
Associated Problems in MR
In addition to the deficits in intellectual functioning and adaptive beh some MR persons have medical problems or associated disabilities. Some of the most common medical problems are epilepsy, hyperactivity, physical handicaps, nutritional disorders etc.
Epilepsy
* 40% of MR persons suffer from epilepsy
* Convulsions vary in their frequency, duration and type depending upon the nature of brain damage
* Fits are more common in persons with severe and profound MR