Intellectual disability, also known as general learning disability and mental retardation (MR), is a condition characterized by significant limitation both in intellectual functioning (reasoning, learning, problem solving) and in adaptive behavior which covers a range of every day, social and practical skills.

Someone with intellectual disability has limitations in two areas. These areas are:

Three areas of adaptive functioning are considered:

1.    Conceptual – language, reading, writing, math, reasoning, knowledge, memory

2.    Social – empathy, social judgment, communication skills, the ability follow rules and the ability to make and keep friendships

3.    Practical – independence in areas such as personal care, job responsibilities, managing money, recreation and organizing school and work tasks


Symptoms of ID will vary based on your child’s level of disability and may include:

If your child has ID, they may experience some of the following behavioral issues:

Some people with ID may also have specific physical characteristics. These can include having a short stature or facial abnormalities.


ID is divided into four levels, based on your child’s IQ and degree of social adjustment.

Mild intellectual disability

Some of the symptoms of mild intellectual disability include:

Moderate intellectual disability

If your child has moderate ID, they may exhibit some of the following symptoms:

Severe intellectual disability

Symptoms of severe ID include:

Profound intellectual disability

Symptoms of profound ID include:



AAMR Classification Scheme

     I.Q.(intelligence quotient) is 100; normal ranges from 90 to 110

·       Border line { IQ 70-80 }

·       mild MR     { IQ 55-70 }

·       moderate MR{ IQ 40-55 }

·       sever MR      { IQ 25-40 }

·       profound MR { IQ below 25 }


Fragile X syndrome

Fragile X syndrome is the most common known cause of an inherited intellectual disability worldwide. It is a genetic condition caused by a mutation (a change in the DNA structure) in the X chromosome.

People born with Fragile X syndrome may experience a wide range of physical, developmental, behavioural, and emotional difficulties, however, the severity can be very varied.

Some common signs include a developmental delay, intellectual disability, communication difficulties, anxiety, ADHD, and behaviours similar to autism such as hand flapping, difficulty with social interactions, difficulty processing sensory information, and poor eye contact

Down syndrome

Down syndrome is not a disease or illness, it is a genetic disorder which occurs when someone is born with a full, or partial, extra copy of chromosome 21 in their DNA.

Down syndrome is the most common genetic chromosomal disorder and cause of learning disabilities in children. People with Down syndrome can have a range of common physical and developmental characteristics as well as a higher than normal incidence of respiratory and heart conditions.

Physical characteristics associated with Down syndrome can include a slight upward slant of the eyes, a rounded face, and a short stature. People may also have some level of intellectual and learning disabilities, but this can be quite different from person to to another.

Prader-Willi Syndrome (PWS)

Prader-Willi syndrome (PWS) is a rare genetic disorder which affects around 1 in 10,000 – 20,000 people. This disability is quite complex and it’s caused by an abnormality in the genes of chromosome 15.

One of the most common symptoms of PWS is a constant and insatiable hunger which typically begins at two years of age. People with PWS have an urge to eat because their brain (specifically their hypothalamus) won’t tell them that they are full, so they are forever feeling hungry.

The symptoms of PWS can be quite varied, but poor muscle tone and a short stature are common. A level of intellectual disability is also common, and children can find language, problem solving, and maths difficult.

Someone with PWS may also be born with distinct facial features including almond-shaped eyes, a narrowing of the head, a thin upper-lip, light skin and hair, and a turned-down mouth.

Fetal alcohol spectrum disorder (FASD)

FASD refers to a number of conditions that are caused when an unborn foetus is exposed to alcohol.

When a mother is pregnant, alcohol crosses the placenta from the mother’s bloodstream into the baby’s, exposing the baby to similar concentrations as the mother.

The symptoms can vary however can include distinctive facial features, deformities of joints, damage to organs such as the heart and kidneys, slow physical growth, learning difficulties, poor memory and judgement, behavioural problems, and poor social skills.

Many cases are also often misdiagnosed as autism or ADHD as they can have similarities.

The World Health Organisation recommends that mothers-to-be, or those planning on conceiving, should completely abstain from alcohol.

Environmental and other causes

Sometimes an intellectual disability is caused by an environmental factor or other causes. These causes can be quite varied but can include:

·       Problems during pregnancy such as viral or bacterial infections

·       trauma before birth, such as an infection or exposure to alcohol, drugs, or other toxins

·       trauma during birth, such as oxygen deprivation or premature delivery

·       Exposure to toxins such as lead or mercury

·       Complications from illnesses such as meningitis, measles or whooping cough

·       Malnutrition

·       Exposure to alcohol and other drugs

·       severe malnutrition or other dietary issues

·       severe cases of early childhood illness, such as whooping cough, measles, or meningitis

·       brain injury

·       And even unknown causes


·       Genetic. Genetic counseling and screening during pregnancy can help parents understand risks and make plans and decisions.

·       Social. Nutrition programs can reduce disability associated with malnutrition. Early intervention in situations involving abuse and poverty will also help.

·       Toxic. Preventing exposure to lead, mercury, and other toxins reduces the risk of disability. Teaching women about the risks of alcohol and drugs during pregnancy can also help reduce risk.

·       Infectious diseases. Certain infections can lead to intellectual disability. Preventing these diseases reduces the risk. For example, rubella syndrome can be prevented through vaccination. Avoiding exposure to cat feces that can cause toxoplasmosis during pregnancy helps reduce disability from this infection.


The intellectual disability calculation is based on VSMS score. The following are used for disability calculation:

1.    VSMS score 0-20: Profound Disability – 100%

2.    VSMS score 21-35: Severe Disability – 90%

3.    VSMS score 36-54: Moderate Disability – 75%

4.    VSMS score 55-69: Mild Disability – 50%

5.    VSMS score 70-84: Borderline Disability – 25%


Intellectual disability is a life-long condition. However, early and ongoing intervention may improve functioning and enable the person to thrive throughout their lifetime. It may also be influenced by underlying medical or genetic conditions and co-occurring conditions.

Once a diagnosis is made, help for individuals with intellectual disability is focused on looking at the individual’s strengths and needs, and the supports he or she needs to function at home, in school/work and in the community.

Services for people with intellectual disabilities and their families provide support to allow full inclusion in the community. Many different types of supports and services can help, such as:

Under federal law (Individuals with Disabilities Education Act, IDEA, 1990), early intervention services work to identify and help infants and toddlers with disabilities. Federal law also requires that special education and related services are available free to every eligible child with a disability, including intellectual disability.

In addition, supports can come from family, friends, co-workers, community members or from a service system. Job coaching is one example of a support that can be provided by a service system. With proper support, people with intellectual disabilities are capable of successful, productive roles in society.

A diagnosis often determines eligibility for services and protection of rights, such as special education services and home and community services. The American Association of Intellectual and Developmental Disabilities (AAIDD) stresses that the main reason for evaluating individuals with intellectual disabilities is to be able to identify and put in place the supports and services that will help them thrive in the community throughout their lives.