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.

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:

• Lack of oxygen (hypoxia).
• Premature birth.
• Other types of brain injury during birth.

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:

• Attention-deficit/hyperactivity disorder (ADHD).
• Autism spectrum disorder.
• Impulse control disorders.
• Mood disorders, especially anxiety disorders and depression.
• Movement disorders.

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.

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