Neurodevelopmental Disorder

Neurodevelopmental disorders are a group of mental conditions negatively affecting the development of the nervous system, which includes the brain and spinal cord. According to the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) published in 2013, these conditions generally appear in early childhood, usually before children start school, and can persist into adulthood.[1] The key characteristic of all these disorders is that they negatively impact a person’s functioning in one or more domains of life (personal, social, academic, occupational) depending on the disorder and deficits it has caused. All of these disorders and their levels of impairment exist on a spectrum, and affected individuals can experience varying degrees of symptoms and deficits, despite having the same diagnosis.

Neurodevelopmental disorders emerge in childhood (although some may not be diagnosed until adulthood) and affect a person’s development. Autism and ADHD are the most common NDs, but these conditions also include intellectual disabilities, learning disorders, and cerebral palsy, among others. While such conditions can affect memory, language, behavior, learning, emotions, and motor skills, people can effectively manage their challenges with the right interventions, support, and accommodations. During the developmental period from infancy through adolescence, neurodevelopment and behavior are intricately related. 

The terms neurodevelopmental and neurobehavioral disorders are used interchangeably to describe a group of disorders with certain basic characteristics that overlap between different disorders (1-5). Neurodevelopmental disorders (or disabilities) have their onset during the developmental period and persist over a person’s lifespan. Intellectual disabilities (also referred to as intellectual developmental disorder), various communication disorders affecting speech and language, autism spectrum disorder, attention deficit hyperactivity disorder, developmental learning disorders, and motor disorders such as developmental coordination disorder and tic disorders are major neurodevelopmental disorders. Some experts use the term neurodevelopmental disabilities “to define chronic disorders that affect central nervous system function during the developmental period in the domains of motor skills, cognition, communication and/or behavior”.The World Health Organization criteria defines neurodevelopmental disorders as “behavioural and cognitive disorders that arise during the developmental period that involve significant difficulties in the acquisition and execution of specific intellectual, motor, or social functions” 

1.1 Intellectual Disabilities

Intellectual disability refers to neurodevelopmental conditions that affect functioning in two areas:

  • Cognitive functioning, such as learning, problem solving and judgement.
  • Adaptive functioning, activities of daily life such as communication skills and social participation.

Additionally, the intellectual and adaptive deficit begin early in the developmental period, typically before age 18 years for diagnosis.
Intellectual disability affects about 1% of the population, and of those about 85% have mild intellectual disability. In high-income countries, 2–3% of children have an intellectual disability.

What is intellectual functioning? 

 Intellectual functioning incorporates the characteristics of intelligence, the abilities assessed by standardized intelligence tests, and the consensus view that intellectual functioning is influenced by other human functioning dimensions and by systems of supports.
 

What is adaptive behavior? 

Adaptive behavior is the collection of conceptual, social, and practical skills that have been learned and are performed by people in their everyday lives, which include the following:
Three areas of adaptive functioning are considered:

  • Conceptual – language, reading, writing, math, reasoning, knowledge, memory.
  • Social – empathy, social judgment, communication skills, the ability to follow rules and the ability to make and keep friendships.
  • Practical – independence in areas such as personal care, job responsibilities, managing money, recreation, and organizing school and work tasks.

Intellectual disability (or ID) is a term used when a person has certain limitations in cognitive functioning and skills, including conceptual, social and practical skills, such as language, social and self-care skills. These limitations can cause a person to develop and learn more slowly or differently than a typically developing person. Intellectual disability can happen any time before a person turns 22 years old, even before birth. Intellectual disability is the most common developmental disability. According to the American Association of Intellectual and Developmental Disabilities, an individual has intellectual disability if he or she meets three criteria:

  • IQ is below 70.
  • There are significant limitations in adaptive behavior in one or more of the following areas: conceptual, social or practical skills (skills that are needed to live, work, and play in the community).
  • The condition manifests itself before the age of 22.

Intellectual disability (ID), once called mental retardation, is characterized by below-average intelligence or mental ability and a lack of skills necessary for day-to-day living. People with intellectual disabilities can and do learn new skills, but they learn them more slowly. There are varying degrees of intellectual disability, from mild to profound. The term “mental retardation” is no longer used, as it’s offensive and has a negative tone.

What is intellectual disability?

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

  • Intellectual functioning. Also known as IQ, this refers to a person’s ability to learn, reason, make decisions, and solve problems.
  • Adaptive behaviors. These are skills necessary for day-to-day life, such as being able to communicate effectively, interact with others, and take care of oneself.

IQ (intelligence quotient) is measured by an IQ test. The average IQ is 100, with the majority of people scoring between 85 and 115. A person is considered intellectually disabled if they have an IQ of less than 70 to 75.
To measure a child’s adaptive behaviors, a specialist will observe the child’s skills and compare them to other children of the same age. Things that may be observed include how well the child can feed or dress themselves; how well the child is able to communicate with and understand others; and how the child interacts with family, friends, and other children of the same age.
 
Intellectual disability is thought to affect about 1% of the population. Of those affected, 85% have mild intellectual disability. This means they are just a little slower than average to learn new information or skills. With the right support, most will be able to live independently as adults. 
Intellectual disability (ID) involves problems with general mental abilities that affect both intellectual functioning (such as learning and reasoning) and adaptive functioning (activities of daily living such as communication and independent living).

 Epidemiology 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 than in women. Approximately 1 – 3 percent of the global population has an intellectual disability—as many as 200 million people. Intellectual disability is significantly more common in low-income countries—16.41 in every 1,000 people. Disabilities overall are more common in low-income countries.The United Nations Development Program estimates that 80 percent of all people with disabilities live in low-income countries. While people with disabilities represent approximately one in 10 people worldwide, they are one in every five of the world’s poorest people.

The prevalence of intellectual disability in developing countries is estimated to range from 10 to 15 per 1000 children; of those, about 85% have a mild intellectual disability. From 1 to 3% of the Western population is estimated to have an intellectual disability. Incidence is challenging to calculate accurately as mild disabilities may be under-recognized until later in childhood. Intellectual disability is reported to peak at the ages of 10 to 14 years and is 1.5 times more prevalent in males than females

Symptoms and Causes - Etiology

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.

While many causes of intellectual disability are not known, the etiology of intellectual disability is mainly divided into genetic abnormalities and environmental exposure. Genetic abnormality can be a single gene mutation, copy number variation, or chromosomal abnormality that causes an inborn error of metabolism, neurodevelopmental defect, and neurodegeneration. Environment exposure can be maternal exposure to toxin/infectious agents, uncontrolled maternal medical conditions, delivery complications, and post-natal trauma and exposure to toxin/infectious agents. The most common known preventable or environmental cause of intellectual disability is fetal alcohol syndrome, the most common chromosomal cause is Down syndrome, and the most common genetic cause is Fragile X syndrome. 

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.

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.
     

Causes of Intellectual Disabilities

  • It can be associated with a genetic syndrome, such as Down syndrome or Fragile X syndrome.
  • It may develop following an illness such as meningitis, whooping cough or measles.
  • It may result from head trauma during childhood
  • It may result from exposure to toxins such as lead or mercury.
  • Other factors that may contribute to intellectual disability include brain malformation, maternal disease and environmental influences (alcohol, drugs or other toxins).
  • A variety of labour- and delivery-related events, infection during pregnancy and problems at birth, such as not getting enough oxygen, can also contribute.

What are the signs of intellectual disability in children?

There are many different signs of intellectual disability in children. Signs may appear during infancy, or they may not be noticeable until a child reaches school age. It often depends on the severity of the disability. Some of the most common signs of intellectual disability are:

  • Rolling over, sitting up, crawling, or walking late
  • Talking late or having trouble talking
  • Slow to master things like potty training, dressing, and feeding themselves
  • Difficulty remembering things
  • Inability to connect actions with consequences
  • Behavior problems such as explosive tantrums
  • Difficulty with problem-solving or logical thinking

In children with severe or profound intellectual disabilities, there may be other health problems as well. These problems may include seizures, mood disorders (anxiety, autism, etc.), motor skills impairment, vision problems, or hearing problems.

Diagnosis and Tests

How is it diagnosed?

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.

How is intellectual disability diagnosed?

Intellectual disability may be suspected for many different reasons. If a baby has physical abnormalities that suggest a genetic or metabolic disorder, a variety of tests may be done to confirm the diagnosis. These include blood tests, urine tests, imaging tests to look for structural problems in the brain, or electroencephalogram (EEG) to look for evidence of seizures.In children with developmental delays, the doctor will perform tests to rule out other problems, including hearing problems and certain neurological disorders. If no other cause can be found for the delays, the child will be referred for formal testing.
 
Three things factor into the diagnosis of intellectual disability: interviews with the parents, observation of the child, and testing of intelligence and adaptive behaviors. A child is considered intellectually disabled if they have deficits in both IQ and adaptive behaviors. If only one or the other is present, the child is not considered intellectually disabled.After a diagnosis of intellectual disability is made, a team of professionals will assess the child’s particular strengths and weaknesses. This helps them determine how much and what kind of support the child will need to succeed at home, in school, and in the community.

 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.

What services are available for people with intellectual disability?

For babies and toddlers, early intervention programs are available. A team of professionals works with parents to write an Individualized Family Service Plan, or IFSP. This document outlines the child’s specific needs and what services will help the child thrive. Early intervention may include speech therapy, occupational therapy, physical therapy, family counseling, training with special assistive devices, or nutrition services. School-age children with intellectual disabilities (including preschoolers) are eligible for special education for free through the public school system. This is mandated by the Individuals With Disabilities Education Act (IDEA). Parents and educators work together to create an Individualized Education Program, or IEP, which outlines the child’s needs and the services the child will receive at school. The point of special education is to make adaptations, accommodations, and modifications that allow a child with an intellectual disability to succeed in the classroom.

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.

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, non-prescription 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.
     

Can intellectual disability be prevented?

Certain causes of intellectual disability are preventable. The most common of these is fetal alcohol syndrome. Pregnant women shouldn’t drink alcohol. Getting proper prenatal care, taking a prenatal vitamin, and getting vaccinated against certain infectious diseases can also lower the risk that your child will be born with intellectual disabilities.In families with a history of genetic disorders, genetic testing may be recommended before conception.Certain tests, such as ultrasound and amniocentesis, can also be performed during pregnancy to look for problems associated with intellectual disability. Although these tests may identify problems before birth, they cannot correct them.

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?

What can I do to help my intellectually disabled child?

Steps to help your intellectually disabled child include:

  • Learn everything you can about intellectual disabilities. The more you know, the better advocate you can be for your child.
  • Encourage your child’s independence. Let your child try new things and encourage your child to do things by themselves. Provide guidance when it’s needed and give positive feedback when your child does something well or masters something new.
  • Get your child involved in group activities. Taking an art class or participating in Scouts will help your child build social skills.
  • Stay involved. By keeping in touch with your child’s teachers, you’ll be able to follow their progress and reinforce what your child is learning at school through practice at home.
  • Get to know other parents of intellectually disabled children. They can be a great source of advice and emotional support.