Intellectual Disability

Intellectual disability is a condition that limits intelligence and disrupts abilities necessary for living independently. Signs of this lifelong condition appear during childhood. Most people with this will need some degree of assistance throughout their lives. Support programs and educational offerings can help with managing symptoms and effects.

Overview

Learn the signs and symptoms of an intellectual disability.

What is intellectual disability?

An intellectual disability is when limitations in your mental abilities affect intelligence, learning and everyday life skills. The effects of this can vary widely. Some people may experience minor effects but still live independent lives. Others may have severe effects and need lifelong assistance and support.

A common misconception is that intellectual disability is just a limitation on intelligence as assessed by a simple IQ test. An IQ test is only one piece of information. Some people have an average or above-average IQ but have trouble with other abilities necessary for everyday life. Other people have lower-than-average IQs but also have skills and abilities that are strong enough that they don’t meet the criteria for intellectual disability, or they meet criteria for a milder form of intellectual disability than an IQ test indicates.

In the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, fifth edition text revision (DSM-5-TR), the formal name for this condition is “intellectual developmental disorder.” Although for many individuals, the exact cause of their intellectual disability is unknown, many cases of intellectual disability happen because of differences in brain development. Less commonly, they can develop because of brain damage from an illness, injury or other events when a person is younger than 18 years old.

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How common is intellectual disability?

Intellectual disability is uncommon but widespread. Worldwide, it affects 1% to 3% of children. It’s slightly more common in men and people assigned male at birth (AMAB) than in women and people assigned female at birth (AFAB).

Symptoms and Causes

What are the symptoms of intellectual disability?

The symptoms of intellectual disability revolve around difficulties in different skill sets, including academic skills, social skills and domestic skills. Intellectual disability affects:

Intelligence-related symptoms

“Intelligence” is the umbrella term for your ability to understand and interact with the world around you. It goes beyond the traditional language and math skills an IQ test measures. Intelligence-related symptoms of intellectual disability can mean you have any of the following:

  • Delayed or slowed learning of any kind (such as in school or from real-life experiences).
  • Slowed reading speed.
  • Difficulties with reasoning and logic.
  • Problems with judgment and critical thinking.
  • Trouble using problem-solving and planning abilities.
  • Distractibility and difficulty focusing.

Adaptive behaviors

Adaptive behaviors revolve around abilities and learned skills you need to live and support yourself independently. Symptoms of adaptive behavior-related limitations can mean you have any of the following:

  • Slower learning of toilet training and self-care activities (bathing, dressing, etc.).
  • Slower social development.
  • Little or no fear or apprehension of new people (lack of “stranger danger” behaviors).
  • Needing help from parental figures or other caregivers with basic daily activities (bathing, using the bathroom, etc.) past the expected age.
  • Difficulty learning how to do chores or other common tasks.
  • Trouble understanding concepts like time management or money.
  • Needing help managing healthcare appointments or medications.
  • Trouble understanding social boundaries.
  • Difficulty with or limited understanding of social interactions, including friendships and romantic relationships.
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What causes intellectual disability?

Intellectual disabilities can happen for many reasons. Experts also suspect that in many cases, there are multiple causes and contributing factors. Causes and contributing factors can influence the development of intellectual disability before or during birth or during the earliest years of childhood.

Prebirth causes or contributing factors include, but aren’t limited to, the following:

  • Genetics and inheritance. Many conditions that cause intellectual disability happen because of genetic mutations. Some of these mutations can be passed from generation to generation. Examples include Down syndrome, Fragile X syndrome or Prader-Willi syndrome.
  • Infections. Some infections — like toxoplasmosis and rubella — can disrupt fetal development, resulting in conditions that can cause intellectual disability, such as cerebral palsy.
  • Teratogens. These are substances that can disrupt fetal development. Examples include alcohol, tobacco, certain medications, radiation exposure and more.
  • Medical conditions. Having certain medical conditions while pregnant can cause developmental differences in a fetus. Those can later result in intellectual disability. Examples include hormonal conditions like hypothyroidism.

Causes that can happen during birth include:

Causes that can happen during early childhood include:

  • Injuries or accidents. These can cause intellectual disability if they result in brain damage.
  • Toxic exposures. Heavy metals like lead and mercury can damage your brain and cause intellectual disability.
  • Infections. Common infections that spread to your nervous system, such as measles or meningitis, can cause intellectual disability.
  • Tumors or growths in the brain. This includes cancers and benign (noncancerous) growths.
  • Medical conditions. Seizures and various types of epilepsy, such as Lennox-Gastaut syndrome, can cause brain damage. That can cause intellectual disability.

What conditions can cause or happen along with intellectual disability?

Many of the differences in the brain that cause or contribute to intellectual disability can also cause or contribute to other conditions or mental health issues. Some of the medical and mental health conditions that can occur alongside intellectual disability (but can also occur in an individual without an intellectual disability) include:

People with intellectual disability due to a specific genetic disorder may also have a higher chance of developing certain health problems related to the underlying condition. Your healthcare provider can tell you more about what conditions your child might have a greater risk of and what you can do to help your child avoid more severe issues.

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Diagnosis and Tests

How is it diagnosed?

Diagnosing intellectual disability is usually a process that takes multiple steps. That’s because diagnosing it requires assessing your intelligence and adaptive behavior capabilities. A key part of the diagnosis is understanding strengths, not just challenges. Knowing someone’s strengths can help tailor treatments and interventions to bolster their strengths and help them cope with challenges.

There are different tests and methods that can help with these assessments, depending on your age. Some forms of testing can identify intellectual disability in very young children. But these tests generally can’t identify how severe it is until they’re old enough for IQ testing and a full assessment of adaptive functioning.

When possible, experts classify intellectual disability severity into four categories:

  • Mild. People with this severity level have an average mental age of between 9 and 12. Their disability may interfere with learning or complex tasks. However, they can often work around these issues, especially with specialized interventions and assistance earlier in life. They also often work and live independently. About 85% of people with intellectual disability have this level of severity.
  • Moderate. People with moderate intellectual disability have an average mental age of 6 to 9 years. They can communicate using simple language. They achieve an education of about an elementary school level. Many can learn to live independently to some degree but will need varying levels of help along the way, such as the kind of support found in a group home.
  • Severe. People with severe intellectual disability have an average mental age of between 3 and 6 years. They use single words, phrases and/or gestures to communicate. They benefit from daily care and support with activities and daily life.
  • Profound. People with this level of intellectual disability have an average mental age of 3 years and below. They usually communicate nonverbally, understanding some gestures and emotional cues. They benefit from 24/7 medical care and support for all activities and aspects of life.

What tests will be done to diagnose this condition?

In addition to the tests and assessments for intelligence and adaptive behaviors, many lab, diagnostic and imaging tests can help with diagnosis. The possible tests depend on your symptoms. Testing can help your provider identify the underlying cause, which can help guide treatment.

Possible tests include:

  • Laboratory testing of blood, urine and more. These can identify underlying causes of intellectual disability or related conditions.
  • Genetic counseling. Identifying genetic conditions that are causing or contributing to intellectual disabilities can help prevent or limit complications related to these underlying conditions.
  • Imaging tests. These are especially helpful with identifying conditions that involve differences in brain structure, such as cephalic disorders.

Other tests may be possible, depending on the condition you have or that a healthcare provider suspects. Your provider can tell you more about the possible tests and which ones they recommend.

Management and Treatment

How is intellectual disability treated?

There’s no way to cure or treat intellectual disability directly. With good treatment, individuals with intellectual disability can have a good quality of life. The treatments focus on helping with adaptive behaviors and life skills.

Treatment types include:

  • Education support and interventions. These can help with changes to educational programs and structure. An example of educational support is an Individualized Education Plan (IEP), which creates a custom educational plan and expectations.
  • Behavioral support and interventions. These kinds of interventions can help with learning adaptive behaviors and related skills.
  • Vocational training. This can help people with intellectual disabilities learn work-related skills.
  • Family education. This can help family and loved ones of those with intellectual disability learn more about intellectual disability and how to support a loved one who has it.
  • Various medications can help with conditions that are related to or happen alongside intellectual disability. While these don’t treat intellectual disability itself, they can help with some of the symptoms that may contribute.
  • Community support. A person and/or their family can contact local government agencies or support organizations. Doing so can help them get access to the services they benefit from, including supports in home or work environments and options for daytime activities.

Prevention

Can intellectual disability be prevented?

Most of the time, experts can’t point to one specific cause of an intellectual disability. Parents shouldn’t blame themselves when this happens. But it might be possible to reduce your child’s risk when you’re pregnant, or while they’re young, by:

  • Following your healthcare provider’s recommendations about taking medications during your pregnancy, and getting all recommended vaccinations (during pregnancy and throughout your child’s life).
  • Limiting exposure to alcohol, nonprescription drugs and tobacco, and environmental toxins like lead.
  • Talking to your provider about preconception genetic counseling if you have a family history of conditions that can cause intellectual disability.

Outlook / Prognosis

What can I expect if my child has intellectual disability?

People who have milder forms of intellectual disability or conditions that cause it may be able to recognize some of the differences between themselves and others. However, a key part of intellectual disability is that it disrupts your ability to fully process and understand what’s happening to you or around you.

Because of that, many individuals with intellectual disability can’t fully understand how this condition affects them. Instead, parental figures or other caregivers are more likely to notice the signs and symptoms of intellectual disability in their child or a child of a close loved one.

Remember that your child will still have goals, desires and strengths. It’s important that you help your child identify these so they can live their best life with the proper support.

People with intellectual disability may also be unable to recognize when others are trying to take advantage of them. Support programs can help teach people with intellectual disability to protect themselves, but caregiver support and oversight are vital to their well-being.

What’s the outlook for intellectual disability?

The outlook for intellectual disability depends on many factors, especially how severe it is, the underlying cause and any other conditions that happen along with it. Your child’s healthcare provider is the best source of information on your child’s outlook and what you can do to help manage their condition.

Most people with intellectual disability will need some form of support throughout their lives. However, there are programs and organizations that can help along the way. Many people with intellectual disabilities can go on to live independently to varying degrees. Depending on their needs, preferences and desires, many have jobs, families and other components that make up everyday life. Overall, with the correct support, individuals with an intellectual disability can have a good quality of life.

Living With

How do I take care of my child if they have intellectual disability?

People with intellectual disability may not be able to make informed choices about their own healthcare or other major life decisions. They may need support from parental figures, loved ones or other caregivers throughout their lifetime.

When should my child see their provider?

The earliest signs of intellectual disability are sometimes detectable during a child’s routine visits with their pediatrician. A standard part of these visits is the assessment of “ages and stages.” This compares your child’s growth and development to what’s expected at their age level. Keep in mind that there are other possible causes for a child to be behind on their pediatric milestones, such as a physical illness, psychiatric illness or specific learning disability.

If you have any concerns about your child’s development and whether they’re at risk for intellectual disability, talk to your child’s pediatrician. They can help you understand the situation better and offer guidance on what you need to do or can do to help your child.

What questions should I ask my doctor?

There are many questions you can ask your child’s healthcare provider that may help you better understand and support your child’s needs. Some of the questions you may want to ask include:

  • How severe is my child’s learning disability?
  • What are their strengths, and what are their challenges?
  • What kinds of programs or support organizations are available in my area or online that can help me or my child?
  • What kind of school programs exist to help my child with their education needs?
  • Will my child be able to live independently, and if so, what kind of services might they need to do so?
  • Does my child have any other conditions, and — if yes — are they treatable?

Additional Common Questions

Mental retardation vs. intellectual disability — what’s the difference?

“Mental retardation” and “intellectual disability” both describe the same concepts. However, “intellectual disability” is the preferred term for multiple reasons:

  • Accuracy. The term “retard” and variations of it come from a French word that means “to slow.” Experts historically used the term “mental retardation” to describe slowed learning or brain function. However, intellectual disability is more complex and involves disruptions in abilities and behaviors. Because of that, “intellectual disability” is the more accurate term.
  • Inclusiveness. Variations of the word “retard” are now largely considered offensive. Widespread misuse of these terms has fueled discrimination and mistreatment. As a result, professional organizations and experts exclusively use “intellectual disability.”
  • Legal recognition. In 2010, the U.S. government enacted Rosa’s law. That law removed all uses of the terms “mental retardation” and “mentally retarded” from government use, law and policies. “Intellectual disability” and “individual with an intellectual disability” became the preferred official and legal terms.

Is ADHD considered an intellectual disability?

No, attention-deficit/hyperactivity disorder (ADHD) and intellectual disability are distinct conditions. They both fall under the same category of developmental disabilities, but they aren’t the same thing. However, many people have both conditions at the same time.

A note from Cleveland Clinic

Intellectual disability is a condition that affects many aspects of a person’s life, but it isn’t the sum total of a person’s being. Education and behavioral support programs also focus on identifying strengths and making the most of them.

If you have a child with an intellectual disability, you may wonder if you were somehow the cause of it. However, intellectual disability is a complicated condition. Multiple factors can cause or contribute to it, so it’s usually not possible to say for certain why it happened (which means you shouldn’t blame yourself if your child develops it). Most importantly, there are numerous support programs and organizations that can help. That way, an individual with intellectual disability has the best chance to have a life that’s as full, happy and fulfilling as any other.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 05/25/2023.

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