Mental Retardation: Definition, Causes & Preventive Measures


Introduction to Mental Retardation

A person with mental retardation or slowness in their mental growth and capacities are called “mentally handicapped” or mentally retarded. They are also referred to as ‘slow developers, slow learners or less intelligent’. Mental retardation is also a term used when a person has certain limitations in mental functioning and skills such as communicating, taking care of himself o request herself and having a social skill. This limitation will cause a child to learn and develop more slowly than a normal child.


  • According to ICD 10, “mental retardation is a condition of arrested or incomplete development of a mind, which is especially characterized by impairment of the skills, manifested during the development period that contributes to cognitive language, motor, and social abilities.
  • According to the  Longman dictionary, “Mental retardation is a disorder characterized by significantly sub averaged general intellectual in IQ 70 or below, with impairment in the adaptive behavior (including thinking, learning, social and occupational, adjustment) and manifested during the development period. (Below 18 years).
  • Mental retardation is a condition of poor development of the brain. This cause the child to have low intelligence. This affects the child’s development, behavior and his social relationships.

Causes of Mental Retardation

Approximately 30% of cases of mental retardation is still unknown, remaining 70% cases of mental retardation are as follows:

  • Genetics: About 5% of mental retardation is caused by heredity factors. Mental retardation may be caused by an inherited abnormality of the genes. And congenital errors of metabolism may also cause mental retardation if they are not diagnosed and treated early. For instance. Development of extra chromosome 18 (Trisomy 18) and down syndrome, is also called mongolism or Trisomy 21, is caused by an abnormality in the development of chromosome 21. It is the most common genetic cause of mental retardation.
  • Problem during pregnancy: About 30% of mental retardation can result when the baby doesn’t develop the mother properly. If the pregnant women who have:
  1. Deficiency such  as folic acid and iodine
  2. Severe malnutrition
  3. Use of substances such as alcohol, nicotine, and cocaine during the early pregnancy
  4. Medical exposure for example anticonvulsants, warfarin, thalidomide, phenytoin, and radiation.
  5. Maternal illness such as toxemia, diabetes, hypoglycemia and hypothyroidism.
  6. Maternal infections e.g. rubella, sexually transmitted diseases, toxoplasmosis, HIV infection. Such infection may spread to the fetus and damage nerve system including the brain.
  7. Fetal distress and hypoxemia during the birth or before the birth.
  • Problem at birth 10%: If a baby has problems during labor and birth such as not getting enough oxygen he/she may have mental retardation. Such as:
  1. Birth-related brain trauma e.g. intracranial haemorrhage
  2. Difficult and complicated delivery
  3. Prolonged labor
  4. Instrumental delivery
  5. Premature birth
  6. Very low birth weight baby
  7. Asphyxia
  8. RH- incompatibility
  • Health problems after birth and during infancy (5%):
  1. Disease like a whooping cough
  2. Brain infection such as encephalitis, meningitis, and tuberculosis
  3. Severe and prolonged malnutrition during the first two years of life
  4. Febrile convulsions
  5. Head injury in early childhood
  6. Exposure to poison like lead or Mercury
  7. Neurological damage or diseases such as frequent seizures
  • Social-cultural and environmental factors  (20%):
  1. Cultural deprivation, lack of  appropriate sensory stimulation for intellectual development
  2. Low socio-economic condition
  3. Inadequate caretaker
  4. Child abuse

Grades/classification of mental retardation:

  1. Mild mental retardation: IQ Level 50-69
  2. Moderate mental retardation: IQ Level 35-49
  3. Severe mental retardation: IQ Level 20-34
  4. Profound: IQ level below 20

Prevalence of mental retardation:

Prevalence of mental retardation is 3-5% out of total retardation, mild make the majority: mild 89%, moderate 7%, severe 3% and profound 1%.


Diagnostic test for mental retardation:

  • History taking/ physical examination.
  • Level of intelligence and ability to learn test:
  • Assessment of vision and hearing
  • Mental status examination
  • Blood test, urine test, thyroid function test
  • Radiological investigation e.g. CT scan or MRI
  • Electroencephalogram (EEG)

The common problem associated with mental retardation:

  • Behaviour problems
  • Convulsion
  • Sensory impairment
  • Other developmental disabilities
  • Speech problems


  • Social isolation
  • Inability to care for self
  • Inability to interact with another person


Individuals with mild to moderate MR are frequently able to achieve some self-sufficiency and leading to happy and fulfilling lives. The outcome is related to the aggressiveness of treatment, personal motivation, opportunity and associated condition.

Preventive measures


  • Improving socio-economic condition
  • Genetic counseling at-risk parent
  • Provide proper nutrition before pregnancy period, folic acid supplements before 6months of pregnancy period
  • Complete Antenatal care
  • Avoid pregnancy before 20 years and after 35 years
  • Avoid exposure of harmful chemical substances
  • Detection and care of risk pregnancy
  • Screening during pregnancy for detecting infection such as HIV, syphilis, hepatitis etc.
  • Termination of baby if any severe problems is seen after consulting a gynaecologist
  • Test such as amniocentesis and Ultrasonography can determine whether a fetus development is normal in the womb
  • Education to the pregnant women about safe motherhood
  • Newborn baby screening
  • Immunization against disease such as routine vaccination, MMR, as well as meningitis, encephalitis
  • Proper nutrition throughout the development period
  • Provide am enriching and stimulating environment for children from infancy.  



Management of Mental Retardation


  • Education and awareness regarding the mental condition
  • Emotional support to both parent and child
  • Avoid the risk of injury
  • Healthy living standard and nutritional supplements
  • Give information to the family and community that mental retardation is not curable, though it can be improved.
  • Do not believe in superstitious treatment which will only worsen the condition, costing a lot of money and waste of time.
  • Provide training to the child e.g. Toilet training, speaking abilities, doing daily works.
  • Vocational training
  • Social education
  • Follow up
  • Group therapy and counselling
  • Intellectual therapy
  • Motivate the family to give training to their child.
  • Encourage the family to help the mentally retarded person to lead as normal a life as possible and to encourage him to do as much as he is able to do.
  • Give your child chores (routine) keep her age, attention span, and abilities in mind.
  • Reassurance to the child and family


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