Intellectual Disability

Intellectual disability is a broad concept encompassing mental retardation or mental deficiency. So-called ‘intelligence’ refers to the ability of understanding, remembering, using information, problem solving, and the capacity for abstract thinking. Individuals with intellectual disabilities are less able compared to people of the same age, and this may become apparent before reaching the age of 18.

Adaptive behavior, or adaptive functioning, refers to the skills needed for a person to live independently. People with intellectual disabilities show limitations in some areas of adaptive behavior and can find it difficult to cope with the challenges of life. Certain skills are important for adaptive behavior and they can be summarized into three categories:

1) The learning of concepts: such as reading and writing, calculation, language understanding and expression, etc.

2) Social skills: interpersonal communication skills, the ability to observe rules, responsibility and self-protection;

3) Daily living skills: such as self-care, use of public facilities, vocational skills

A person is regarded as having an ‘intellectual disability’ if significant limitations are shown in two or more areas of adaptive behavior before the age of 18. After reaching adulthood, brain damage caused by accident or illness and memory loss from old age is not considered as intellectual disabilities.

Intellectual disability is not a disease and therefore cannot be cured by medication. However, individuals with intellectual disabilities are still able to learn – they often just require more time and effort.

Congenital factors

  • Abnormalities with the X or Y chromosome, such as Down Syndrome
  • Genetic factors
  • Metabolic disorder

Acquired factors

  • Problems during pregnancy (such as German measles or diabetes), taking the wrong medication, nutritional deficiencies, alcoholism, or the result of X-ray radiation
  • Problems at birth, such as asphyxia
  • High fever during infancy, virus infection (such as meningitis or jaundice) causing brain malfunction, accident, brain injury, etc.
· Mild mental retardation (IQ: 50-69)

About 85% of people with intellectual disabilities fall into this class. Children can develop social and communication skills during the pre-school period (0-5 years old). Sensory impairment, as compared with normal children, is not always obvious until they are older. In adulthood, they are able to learn social and vocational skills and to maintain minimum dependence. However, they will need support and assistance when facing social or economic pressures. Individuals with mild intellectual disabilities can live independently in the community if appropriate education and training are given to them in the early stages.

· Moderate mental retardation (IQ :35-49)

This group accounts for 10% of the population with intellectual disabilities. Individuals develop the ability to speak during the pre-school period. They can learn to communicate through social skills training, and may also benefit from vocational training. With appropriate supervision, they may have the ability to take care of themselves and learn to commute to and from a familiar place. In adulthood, they may be able to engage in non/semi-technical work in sheltered workshops under close supervision. They need help to adapt to a normal social life and to cope with pressure.

· Severe mental retardation (IQ:20-34)

This classification accounts for 3-4% of those with intellectual disabilities. Individuals display very limited language skills development during the pre-school period; however, they are still able to benefit from basic self-care training. In adulthood, they will require close supervision to undertake simple tasks. In addition, they may also need special nursing care for their other disabilities.

· Profound mental retardation (IQ: Below 20)

This condition accounts for only about 1% to 2% of cases. Individuals have very limited sensory capacity in the early stage. They can only learn some simple self-care and communication skills within a highly structured environment with constant supervision. More positive progress can be made if a good relationship has been fostered with their caregiver.

  • Individuals with intellectual disabilities have difficulty in learning the use of language, communication, and understanding abstract concepts.
  • Lower levels of concentration, easily distracted, poor memory, difficulties in memorizing or consolidating what they have learned, and flexibly using existing knowledge.
  • Weak comprehension and understanding could affect their motivation and initiative to learn. External stimulus and encouragement are vital.
  • Due to weaker intellectual and analytical capabilities, individuals with intellectual disabilities need clearer and more specific guidelines and to learn at their own pace
  • They need more time and opportunity to learn compared to others of the same age.
  • They have relatively weak language and communication skills. We need to take the initiative to speak to them and pay closer attention to their gestures, facial expressions and sound pronunciation, as these are all ways in which they communicate.
  • Encourage them to try and provide opportunities to help them build confidence and self-esteem.

1. (American Association on Intellectual and Developmental Disabilities)
3. ‘To Know More – Understanding the mentally handicapped‘ (2004) Hong Kong: Hong Chi Association, p. 2.
4. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 3rd edition.