What Is an Intellectual Disability?

Portrait of young man with special needs outdoors in town.

Halfpoint Images / Getty Images

Table of Contents
View All
Table of Contents

What Is an Intellectual Disability?

An intellectual disability is a neurodevelopmental condition that develops in childhood. It affects your capacity to learn and retain new information, and it also affects everyday behavior such as social skills and hygiene routines. People with this condition experience significant limitations with intellectual functioning and developing adaptive skills like social and life skills.

An IQ test determines whether a person has an intellectual disability. IQ scores lower than 70 indicate an intellectual disability. The severity of the condition can range from mild to profound.

  • Mild intellectual disability: A majority of people with intellectual disability experience a mild to moderate form. They can learn practical life skills and function daily with minimal support. However, they might struggle to understand how things work and develop social skills.
  • Severe intellectual disability: With severe intellectual disability, your child might experience significant developmental delays. They need more support than children with mild intellectual disabilities and have limited communication skills.
  • Profound intellectual disability: Children with profound intellectual disability often find it especially difficult to communicate and have difficulty performing physical activities. They are also more likely to develop associated medical conditions. They typically require round-the-clock care and support.

Children with a mild intellectual disability can live a fully functioning life with proper support. However, children with a severe intellectual disability require more extensive and constant support. This condition used to be referred to as mental retardation, which took on a negative connotation in society and was replaced with intellectual disability. This term is less offensive and communicates the severity of the condition.

Intellectual disability is one of the most common developmental disabilities in children. It's estimated that around 6.5 million Americans have an intellectual disability. 

Types of Intellectual Disabilities

There is a range of conditions typically classified as intellectual disability. Some of the most common include:

  • Fragile X syndrome: This is a genetic condition caused by a mutation in the X chromosome. It is the most common type of inherited intellectual disability. Its symptoms include speech problems, sensory issues, and behavioral changes.
  • Down syndrome: Down syndrome is one of the most common forms of intellectual disability. The condition causes a person to develop an extra chromosome which changes how the brain and body develop. People with Down syndrome have distinct physical features that are a marker of the condition. They might have a flattened face and nose, small ears, hands and feet, a short neck, and almond-shaped eyes. They typically have lower than average IQs and experience developmental delays.
  • Prader-Willi syndrome (PWS): This is a rare genetic condition that affects a child's mental and physical development. A key feature of this disorder is hyperphagia, otherwise known as chronic eating. This causes many children with the condition to develop obesity. Other symptoms include weak muscle tone, behavioral problems, and intellectual delays.
  • Fetal alcohol spectrum disorders (FASDs): Fetal alcohol spectrum disorders refer to a range of conditions caused by alcohol abuse while pregnant. However, consuming even small amounts of alcohol when pregnant could cause the condition. Common symptoms of FASDs include visual or hearing problems, abnormal facial features, lower IQ, and cognitive difficulties.
  • Autism: Autism is a neurodevelopmental condition that causes social, behavioral, and communication challenges. It's unclear what causes the condition to develop, and however, a combination of genetic and environmental factors is suspected. Some common symptoms include being unable to make eye contact, lack of interest in social interactions, non-verbal communication, and sensory sensitivities.

Symptoms of an Intellectual Disability 

Symptoms of intellectual disability will typically start to surface in early childhood. In some cases, these signs might be physical. You might notice your child has an unusually large or small head, abnormalities with their hands or feet, or other physical differences. However, this isn't always the case.

Children who appear physically healthy and normal could also have an intellectual disability. Children who have severe intellectual disability might begin to exhibit symptoms at an earlier age than those with a milder form. If you are worried your child might have an intellectual disability, here are some of the early signs to look out for: 

  • Difficulty speaking 
  • Beginning to move around later than other children 
  • Trouble following simple instruction 
  • Struggling to develop social skills 
  • Delayed motor skills 
  • Seizures 
  • Temper tantrums 
  • Aggressive behavior 
  • Struggling to remember things 
  • Difficulty problem solving 
  • Difficulty developing social skills 
  • Difficulty expressing emotions 
  • Being unable to carry out personal care like getting dressed or taking a bath 

Identifying an Intellectual Disability 

To diagnose an intellectual disability, the following criteria must be met:

  • Limited intellectual functioning: This is typically measured with an IQ test. A test score lower than 70 is usually indicative of limited intellectual functioning. 
  • Limited adaptive skills: Here, a person with an intellectual disability will struggle with social and practical skills needed for daily functioning. These include conceptual skills like reading or writing, social skills like communication or problem solving, and practical skills like eating, walking, or getting dressed. 
  • The onset of symptoms before the age of 18: This condition typically develops in childhood. While it ranges in severity, some early signs delayed motor skills, struggle with problem-solving, difficulty remembering things, and delayed speech. 

Some research shows that about 20-35% of people who have an intellectual disability are also likely to develop other mental health conditions like anxiety or depression. In determining your child's diagnosis, several tests might be ordered by your healthcare provider and the team of specialists taking care of your child. These tests include: 

  • Neurological tests such as an electroencephalogram (EEG) or magnetic resonance imagining (MRI) to determine if there are any abnormalities in the brain
  • Genetic tests to help identify if there is an inherited disorder like Fragile X syndrome that could cause intellectual disability
  • General medical tests depending on the symptoms your child is exhibiting
  • Special education tests 
  • Developmental screening tests to determine your child's level of intellectual and social functioning
  • Prenatal screening to determine if there are any developmental challenges while a parent is still pregnant
  • A hearing evaluation in case a hearing problem is responsible for the impaired intellectual functioning and not an intellectual disability. 

Causes of Intellectual Disabilities 

Anything that interferes with the proper growth and development of a child could cause an intellectual disability. It can be challenging to identify the specific cause of your child's intellectual disability in some cases. Several culprits could be responsible for the development of an intellectual disability. Some of the most common include: 

  • Pregnancy complications 
  • Genetics 
  • Childhood illnesses that affect brain development 
  • Environmental factors like pollution
  • Severe emotional or physical abuse 
  • Malnutrition 
  • Being born prematurely 
  • Chromosomal abnormalities like Down syndrome 
  • Head injuries 

Treatment for an Intellectual Disability  

There is no one-fix treatment for intellectual disability. The condition is a lifelong one that will need continuous management. The key to proper treatment is early intervention. Getting an accurate diagnosis and treatment plan once you notice the condition's early symptoms is crucial.

Treatment comes in the form of support and care to improve the daily functioning of a person living with the condition. There is presently no cure for intellectual disability. The main aim of treatment is to improve the daily functioning of a person with this condition. 

Coping With an Intellectual Disability

It's essential to remember that children with intellectual disabilities have the same needs as any other child. Keeping them amongst their peers and exposing them to regular childhood activities is vital for their development. Parents of children with intellectual disabilities often feel the need to keep them secluded to protect them from ridicule or bullying. However, this doesn't help with the development of their social skills.

If you are the parent of a child living with an intellectual disability, here are some things you could do to make sure your child is living a healthy and fully functioning life: 

  • Join a support group: A support group of parents and people living with this condition can provide a wealth of reliable information and emotional support. 
  • Learn more about the condition: It's essential to take time to do your research and learn as much about the condition your child is dealing with as you can. 
  • Don't rush the process: Intellectual disability is a lifelong condition. The process for your child's treatment can take a long while before you see any progress. In severe cases, don't expect your child to make rapid progress. 
  • Stay social: It's vital to maintain your child's social life if they've been diagnosed with the condition. Isolating them can exacerbate their symptoms. 
  • Take part in their treatment: During your child's treatment, they'll work with a host of child care specialists to improve their functioning. It's crucial to be a part of this process. 
11 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Institute of Child Health and Human Development. About intellectual and developmental disabilities(IDDs).

  2. Boat TF, Wu JT, Disorders C to E the SSIDP for C with M, et al. Clinical Characteristics of Intellectual Disabilities. National Academies Press (US); 2015.

  3. National Down Syndrome Society (NDSS). What is an intellectual disability.

  4. Stefanovic S, DeMarco BA, Underwood A, Williams KR, Bassell GJ, Mihailescu MR. Fragile X mental retardation protein interactions with a G quadruplex structure in the 3'-untranslated region of NR2B mRNAMol Biosyst. 2015;11(12):3222-3230. doi:10.1039/c5mb00423c

  5. Cleveland Clinic. Fragile x syndrome: diagnosis, symptoms & treatment.

  6. Centers for Disease Control and Prevention. Facts About Down Syndrome.

  7. Elena G, Bruna C, Benedetta M, Stefania DC, Giuseppe C. Prader-willi syndrome: clinical aspects. Journal of Obesity. 2012;2012:1-13. doi:10.1155/2012/473941

  8. Mukherjee RAS. Fetal alcohol spectrum disorder: an overviewJournal of the Royal Society of Medicine. 2006;99(6):298-302. doi:10.1258/jrsm.99.6.298

  9. MSD Manual Professional Edition. Intellectual disability - pediatrics.

  10. Shree A, Shukla PC. Intellectual Disability: Definition, classification, causes and characteristicsLear Commun. 2016;7(1):9. doi:10.5958/2231-458X.2016.00002.6

  11. MSD Manual Consumer Version. Intellectual disability - children’s health issues.

By Toketemu Ohwovoriole
Toketemu has been multimedia storyteller for the last four years. Her expertise focuses primarily on mental wellness and women’s health topics.