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Many would define mental retardation as a disability or disease; however mental retardation in medical terms refers to a functional state with limitations in both aptitude and ability. These are people who score below 70 in a standard IQ test. In ancient Greek, the value of human beings was associated with the ability to reason and so anyone who couldn’t was not considered a human being and hence they were treated as social misfits. Romans were the first to come up with a law that criminal punishment was for those who committed crime knowingly for they associated mental retardation with infancy. There are documented cases in England when property of the retarded was confiscated by the king so as to protect the property. This concept was adopted by colonialists from England and America where welfare benefits were given to those considered less intellect. Tests were performed to determine who qualified. People with mental retardation have come from far in struggle for justice to be accorded treatment and special education.


According to World Health Organization (n. d), causes of mental retardation are classified into three categories, Causes before birth (prenatal), causes during birth (perinatal) and causes during infancy and childhood (postnatal).Prenatal causes are chromosomal disorders including Downs ‘syndrome, Fragile X syndrome, Prader-Willi syndrome and Klinefelter’s syndrome. Downs syndrome is also known as Trisomy 21 in which a child inherits 47 chromosomes instead of 46. This extra genetic material leads to delay in physical and mental development. Downs syndrome cannot be prevented but can be detected before birth. Fragile X syndrome is caused by changes in FMR1 gene due to repetitions of three genetic codes CGG on the X chromosome. This is the gene that makes a protein needed for proper rain development. Fragile X syndrome is the most inherited mental disorder. Symptoms are more severe in males than females since males only inherit one X chromosome.

Prader-Willi syndrome is a congenital disease caused by a gene missing on chromosome 15 characterized by decreased mental capacity, sex glands that produce little or no hormones, decreased muscle tone and obesity. Most patients have no family history of this syndrome. Klinefelter’s Syndrome is a condition affecting males due to presence of an extra X chromosome to have XXY. This affects language, physical and social development and also causes infertility. Treatment is available to enable young boys lead normal sex lives.

Another form of prenatal causes results from single gene disorders like inborn errors of metabolism which include galactosemia, mucopolysaccharidosis and galactosemia, hypothyroidism, Tay-Sachs syndrome, neuro-cutaneous syndromes including tuberous sclerosis and neurofibromatosis, brain malformations such as myelomeningocele, genetic microcephaly and hydrocephalus, Lawrence-Moon Biedl syndrome. Galactosemia is a condition in which the body lacks the enzyme to metabolize galactose. This results into accumulation of galactose that leads toxicity that causes eye cataracts, mental retardation, stunted growth, kidney failure and liver damage. It can cause death if not treated. Phenylketonuria is an amino acid disorder whereby the body does not utilize phenylalanine. This causes accumulation of phenylalanine in the blood causing mental retardation, eczema, behavior problems and seizures if left untreated. Mucopolysaccharidosis is an inherited metabolic disorder affecting mucopolysacharide that is deposited in the blood due to lack of enzyme. However, not all types of this disorder cause mental retardation.

Hypothyroidism results when the thyroid gland makes insufficient thyroid hormone. Tay-Sachs is caused by agene defect on chromosome 15 which leads to lack of hexosaminidase A, a protein that breaks down gangliosides. Gangliosides accumulate in the brain causing nerve damage. Tuberous sclerosis is a genetic disorder that causes tumors in the brain, eyes, heart, kidneys, lungs and skin. This leads to mental retardation, developmental delays and autism. Neurofibromatosis is an inherited disorder that affects the spinal cord, brain, skin and nerves through formation of tumors.

Myelomeningocele occurs before birth when the backbone and the spinal canal do not close before birth, (Kanashiro & Zieve, 2009). Microcephaly is a condition where the head of an individual is smaller than normal their age and sex either by genetic inheritance or severe malnutrition. This happens when brain growth is slow or does not occur. Hydrocephalus is accumulation of excess fluid in the skull which causes the brain to swell causing damage to brain tissue. Lawrence-Moon-Biedl syndrome is an autosomal recessive condition accompanied by mental retardation, eye cataracts, kidney abnormalities, obesity and squint eye.

Iodine deficiency, folic acid deficiency, severe malnutrition during pregnancy, use of alcohol, cocaine and nicotine in early pregnancy, exposure to dangerous chemicals, medications including thalidomide in early pregnancy, infections like syphilis and rubella and rhesus incompatibility are prenatal causes of mental retardation due to  environmental conditions.

Perinatal causes usually might happen in the third trimester or during labor due to pregnancy complications, kidney diseases, diabetes, heart disease and placental dysfunction of the mother or complicated delivery, birth asphyxia, birth trauma, very low birth weight or severe prematurity. Severe jaundice, septicemia or hypoglycemia can occur during the neonatal period which is the first four weeks after birth causing severe brain damage to the infant.

Post natal causes include brain infections including tuberculosis, bacterial meningitis or Japanese encephalitis, severe head injury which may affect the brain, persistent lead exposure that poisons the brain and central nervous system, extended malnutrition might affect physical and mental development and gross under simulation.

Facts and figures

About 3% of American population suffers from mental retardation which is lower compared to developing countries like Sri Lanka with 12%. This difference in figures is because in developing countries many live under poverty level exposing new babies to severe malnutrition and accessibility to health facilities is poor. High cases of mild mental retardation have been reported than severe mental retardation mainly in rural areas. Most would think that mental retardation is an illusion coupled with imagination but this is a neurological disorder caused by brain damage. Also mental retardation cannot be spread from one person to another, the reason why many people avoid contact with mentally retarded people. What they should understand is that mental retardation is different from mental illness. What mentally retarded people require is attention, patience and love from their families as opposed to locking them from the society in asylums. These are also humans and they also crave for family, love and attention, (Gaikwad, n. d).

Some cases of mental retardation can be prevented while others are non avoidable and only a medical doctor can diagnose cases of mental retardation. Mentally retarded people are not the same as each person is affected differently due to different levels of exposure to mental retardation causes. Due to this, mentally retarded people have different abilities and capabilities; they are those who can lead an almost normal life and those who are totally dependent. Sometimes mentally retarded persons may act violently or dangerously because of the low IQ, these people respond in an abnormal way to situations. Many non governmental organizations have come up with away to help improve mental ability of the mentally retarded persons by organizing vocational trainings which help to give some level of independence to the affected persons.

Scientific research indicates that when a mentally retarded people are properly trained with a lot of patience, they work better with low error incidences and enjoyment of work than normal people. This has been associated to higher enthusiasm in mentally retarded people because they rarely get bored as in the case of normal people. Due to this fact, many industries are hiring more trained mentally retarded persons especially in assembling of motor products. Such a case was witnessed when people with mental retardation were involved in assembly of Apollo 11, the vessel travelled to the moon with several scientists on board, (World Health Organization).

Even with all the se facts, people with mental retardation are stigmatized by communities influencing their families to result to hiding them. Their families too lead a miserable life because of social stigma. To prevent this, awareness should be created in the communities and families so that these people feel appreciated and loved. Training should also be conducted at family level to enable the families know how to take care of mentally retarded people. Government policies should include rights to education treatment and care for such cases.





Gaikwad, M. (n. d), Mental retardation facts, retrieved on February 5, 2011.

Kanashiro, K. N. and Zieve, D. (2009), Myelomeningocele, NCBI Retrieved on February 5, 2011

World Health Organization (n. d), Mental Retardation, Retrieved on February 5, 2011.


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