Intellectual disability (ID), once called mental retardation, is characterized by below-average intelligence or mental ability and a lack of skills necessary for day-to-day living. People with intellectual disabilities can and do learn new skills, but they learn them more slowly. There are varying degrees of intellectual disability, from mild to profound.
Someone with intellectual disability has limitations in two areas.

These areas are:
Intellectual functioning - Also known as IQ, this refers to a person’s ability to learn, reason, make decisions, and solve problems. Adaptive behaviors - These are skills necessary for day-to-day life, such as being able to communicate effectively, interact with others, and take care of oneself.


The most common symptoms are -

  • Failure to meet intellectual developmental markers
  • Persistence of infantile behavior
  • Lack of curiosity
  • Decreased learning ability
  • Inability to meet educational demands of school


Causes of mental retardation are numerous, but a specific reason for mental retardation is determined in only 25 percent of cases.
Failure to adapt normally and grow intellectually may become apparent early in life or, in the case of mild retardation, may not become recognizable until school age or later. An assessment of age-appropriate adaptive behaviors can be made by the use of developmental screening tests. The failure to achieve developmental milestones is suggestive of mental retardation.
A family may suspect mental retardation if motor skills, language skills, and self-help skills do not seem to be developing in a child or are developing far more slowly than among the child's peers.
Causes of mental retardation can be roughly broken down into several categories:

  • unexplained (the largest category)
  • trauma (prenatal and postnatal) such as oxygen deprivation before, during or after birth
  • infection (congenital and postnatal)
  • Chromosomal abnormalities
  • Genetic abnormalities and inherited metabolic disorders
  • metabolic disorders
  • toxins such as lead or mercury poisoning
  • nutritional deficits such as severe malnutrition
  • environment


In order to develop an appropriate treatment plan, an assessment of age-appropriate adaptive behaviors should be made using developmental screening tests. The objectives of these tests are to determine which developmental milestones have been missed. The primary goal of treatment is to develop the person's potential to the fullest. Special education and training may begin as early as infancy. Attention is given to social skills to help the person function as normally as possible.
It is important for a specialist to evaluate the person for coexisting affective disorders that may require treatment. Behavioral approaches are important in understanding and working with mentally retarded individuals.