What Is an Intellectual Disability?

Intellectual disability (or ID) is a term used when a person has certain limitations in cognitive functioning and skills, including communication, social and self-care skills. These limitations can cause a child to develop and learn more slowly or differently than a typically developing child. Intellectual disability can happen any time before a child turns 18 years old, even before birth.

Intellectual disability is the most common developmental disability.

The international definition for intellectual disability has three criteria:

  • Significant limitations in intelligence (classified as an IQ level of 70 or below)
  • Significant limitations in the skills needed to live and work in the community, including difficulties with communication, self-care, social skills, safety, and self-direction.
  • Limitations in intelligence and living skills are evident in the developmental period (i.e. before the person is aged 18 years)

Type of disabilities:

Fragile X Syndrome

Fragile X is a genetic condition that affects a person's development, especially behavior and the ability to learn. In addition, Fragile X can affect communication skills, physical appearance and sensitivity to noise, light, or similar stimulus. Fragile X is the most common form of inherited intellectual and developmental disability.

Down Syndrome

Down syndrome describes a set of cognitive and physical symptoms that result from having an extra copy or part of a copy of chromosome 21. Down syndrome is the most frequent chromosomal cause of mild to moderate intellectual disability, and occurs in all ethnic and economic groups.

Autism Spectrum Disorders

Autism Spectrum Disorder (known as ASD or, more generally, autism) is a complex neurological and developmental condition that affects how a person learns, communicates and interacts with others. Different people with autism can have different symptoms, which is why it's known as a "spectrum" disorder. Autism affects the structure and function of the brain and nervous system.

Other Intellectual Disabilities

There are many other types of intellectual disabilities-most have known causes, while others remain unknown. Some happen before birth, such as Fetal Alcohol Syndrome or Apert Syndrome; others happen as a baby is being born or soon after birth. Other causes of intellectual disability occur when a child is older; these might include serious head injury, stroke, or certain infections.

How Does an Intellectual Disability Happen?

Intellectual disability—formerly known as mental retardation—can be caused by injury, disease, or a problem in the brain. For many children, the cause of their intellectual disability is unknown.

Some causes of intellectual disability—such as Down syndrome, Fetal Alcohol Syndrome, Fragile X syndrome, birth defects, and infections—can happen before birth. Some happen while a baby is being born or soon after birth.

Other causes of intellectual disability do not occur until a child is older; these might include severe head injury, infections or stroke.

What Are the Most Common Causes?

The most common causes of intellectual disabilities are:

Genetic conditions. Sometimes an intellectual disability is caused by abnormal genes inherited from parents, errors when genes combine, or other reasons. Examples of genetic conditions are Down syndrome, Fragile X syndrome, and phenylketonuria (PKU).

Complications during pregnancy. An intellectual disability can result when the baby does not develop inside the mother properly. For example, there may be a problem with the way the baby’s cells divide. A woman who drinks alcohol or gets an infection like rubella during pregnancy may also have a baby with an intellectual disability.

Problems during birth. If there are complications during labor and birth, such as a baby not getting enough oxygen, he or she may have an intellectual disability.

Diseases or toxic exposure. Diseases like whooping cough, the measles, or meningitis can cause intellectual disabilities. They can also be caused by extreme malnutrition, not getting appropriate medical care, or by being exposed to poisons like lead or mercury.

We know that intellectual disability is not contagious: you can’t catch an intellectual disability from anyone else. We also know it’s not a type of mental illness, like depression. There are no cures for intellectual disability. However, children with intellectual disabilities can learn to do many things. They may just need take more time or learn differently than other children.

How Common Are Intellectual Disabilities?

   The prevalence rate of Persons with Disabilities (PwDs) in Singapore is as follows:

 POPULATION GROUP

 APPROXIMATE PREVALENCE RATE

 Student population

 2.1% of student populationa

 18–49 years

 3.4% of resident populationb

 50 years and above

 13.3% of resident populationc

 

  • Persons with sensory (blindness and deafness) and physical disabilities constitute half of the disability group. The other half comprises those with Intellectual Disabilities, Autistic Spectrum Disorder and other types of disabilitiesd.
  • As part of efforts to better support PwDs, the Ministry of Social and Family Development (MSF) is working with the Department of Statistics (DOS) to include disability-related questions in the upcoming population census to be conducted in 2020. Data collected from the census will enable government agencies to better plan services and programmes for different groups of PwDs.

aSource: Ministry of Education. This is based on the number of reported cases of students with sensory impairment, physical impairment, autism spectrum disorder and intellectual disability. The total student population is put at approximately 460,000.

bSource: National Council of Social Service. Based on a random sampling of 2,000 Singapore citizens and permanent residents aged 18 and above done by NCSS in 2015, the self-reported disability prevalence rate was 3.4% for those aged 18–49 years old. This includes those who acquired disabilities due to accidents and illness. The resident population is put at approximately 3.9 million.

cSource: National Council of Social Service. Based on a random sampling of 2,000 Singapore citizens and permanent residents aged 18 and above done by NCSS in 2015, the self-reported disability prevalence rate was 13.3% for those aged 50 years and above. This includes those who acquired disabilities due to accidents, illness and old age. The resident population is put at approximately 3.9 million.

dEstimated based on the profile of the persons with disabilities who are served under SG Enable's administered schemes and services (Sep 2016).

 

Sources: Special Olympics International, Institute of Mental Health, Ministry of Social & Family Development