Intellectual Disability(ID) / Intellectual Developmental Disorder

Intellectual Disability (ID),also called Intellectual Development Disorder (IDD) formerly known as Mental Retardation (MR), is a generalized neurodevelopmental disorder characterized by significantly impaired intellectual and adaptive functioning. It is defined by an IQ score below 70 in addition to deficits in two or more adaptive behaviors that affect everyday, general living. It means a condition of arrested or incomplete development of mind of a person that is characterized by 'sub-normality of intelligence'.

Children with CP have uncoordinated or spastic movements, so they are referred to as 'Spastic Children'. These children have multiple handicaps, hearing impairments, speech defects, epilepsy, etc. These children may have difficulty with fine motor tasks, such as writing or cutting with scissors; experience trouble with maintaining balance and walking; or be affected by involuntary movements, such as uncontrollable writhing motion of the hands or drooling. The symptoms differ from one child to the next, and may even change over time in the same child. Cerebral palsy is classified into four broad categories - spastic, athetoid, ataxic, and mixed forms -- according to the type of movement disturbance.


The Intellectually disabled child has delayed development & exhibits delayed milestones. The baby sleeps longer, has feeding difficulties, lacks control over bowel movements. They have delays in following areas :

  • Delays in oral language development
  • Deficits in memory skills
  • Difficulty learning social rules
  • Difficulty with problem solving skills
  • Delays in the development of adaptive behaviors such as self-help or self-care skills
  • Lack of social inhibitors
  • Like all Disabilities, Intellectual Disability can also be Congenital or Acquired.

Congenital- Down's Syndrome (Mongolism)


Down's syndrome is associated with chromosomal abnormality. There is an extra chromosome present. The child with Down's syndrome is easy to recognize because of his physical features. The nose is short and flat. The eyes have an upward slant giving them an oriental appearance, thus giving them the name, Mongol. The IQ level rarely exceeds 50, but because of their placid temperament, they are easy to train and educate.


In acquired cases of Intellectual Disability, the child is born quite normally, but due to some disease or an accident, there is permanent brain damage, which results in mental deficiency.

The classification is done on the basis of IQ (Intelligence Quotient). There are many definitions of intelligence, but according to Binet and Simon, who are pioneers of IQ tests -

Intelligence is judgment, good sense, initiative, the ability to comprehend and to reason well and to adapt oneself to circumstances.

Intelligence Quotient(IQ)

IQ = {

     Mental Age(MA)

} X 100 

Chronological Age (CA)


IQ represents the degree of brightness possessed by an individual and it is obtained through tests based on reasoning ability. They are in the form of questions, puzzles and exercises

Chronological Age (CA)

Mental age is an individual's level of performance, whereas chronological age is his physical age. A child of 8 years who has mental age of 4 will have an IQ of 50. A normal or an average child's IQ is 90-110. 

Categories of Mental Retardation Level

  70 - 89 borderline / Slow learner
  52 - 69 mild
  36 - 51 moderate
  20 - 35 severe
  Under 20 profound


Remember that we cannot label a child as Intellectually Disabled on the basis of IQ alone because performance is always a decisive factor and depends on combination of IQ and application. Training and support from home affect application. Though the child's IQ maybe low, proper management, appropriate educational plan can make the child a useful member of Society.