Which of the following are common types of intellectual and developmental disabilities?

Understanding I/DD

Intellectual and developmental disabilities (I/DD) are disorders that begin in childhood. They have many causes and symptoms.

Intellectual disabilities are disorders that involve difficulties in intellectual functioning and adaptive behavior and begin before the age of 18. Intellectual functioning involves mental tasks such as learning, reasoning, problem-solving, and so on. It is assessed using an IQ test and is measured in terms of mild, moderate, or severe[1]. Adaptive behavior includes conceptual, social, and practical skills. People who struggle with adaptive behavior may show difficulties with literacy, money management, schedules and time, interpersonal relationships, daily personal care activities, and more [2].

Developmental disability is a broad term that encompasses intellectual disabilities and other lifelong disabilities that begin in childhood before age 22. Developmental disabilities affect intellectual functioning, physical functioning, or both [3]. Examples include Down syndrome, Autism Spectrum Disorder, cerebral palsy, Fragile X Syndrome, and more [4]. Someone with a developmental disability may or may not also have an intellectual disability. Some developmental disabilities may be diagnosed before or shortly after birth, and others may not be diagnosed until later in childhood. Developmental monitoring and screening by a pediatrician can assess whether or not your child is reaching developmental milestones as expected.

Fact Sheets and Frequently Asked Questions

The Centers for Disease Control and Prevention provide a fact sheet on intellectual disabilities in English and Español

The Centers for Disease Control and Prevention provide information on developmental disabilities, including developmental milestones and developmental monitoring and screening. This information is also available en Español. 

The Arc offers an introduction to intellectual disability. 

Other Resources

Your local Children’s Developmental Services Agency coordinates early intervention services for infants and toddlers up to age 3 who have special needs. 

Alliance Health offers a list of links to I/DD resources in various areas of North Carolina. 

Advocacy and Social Connections

The Arc runs a public policy and legal advocacy page with toolkits and fact sheets to inform people about Medicaid, the Affordable Care Act, and Social Security. 

The North Carolina Council on Developmental Disabilities works to involve people with I/DD and their families in legislative and public policy advocacy.

Wake Network of Care offers a list of links to social and recreational programs for people with I/DD in Wake County and surrounding areas. 

References

Intellectual disability (ID) is impaired development of learning, reasoning, social, and life skills. It often becomes apparent at birth or during childhood and continues through adulthood. This condition occurs in varying degrees and can result from genetic, environmental, or unknown factors.

For many decades, the medical establishment and the general public unkindly referred to affected individuals as "feeble-minded," "moron," "idiot," and "imbecile." In the 1960s, the American Association on Intellectual and Developmental Disabilities (AAIDD) and lawmakers adopted the term “mentally retarded," which experts considered to be more sensitive at the time.

The term "intellectual disability" came about because of Rosa’s Law, passed in 2010 and named after a young girl with ID.

This article will review ID, its causes, diagnosis, related conditions, and tips for parents.

What Does Intellectual Disability Mean?

According to the AAIDD, intellectual disability is "a disability characterized by significant limitations in both intellectual functioning and in adaptive behavior." Intellectual functioning includes abilities such as learning, practicing judgment, and problem solving. Adaptive behavior includes activities of daily functioning, such as living independently and communicating.

ID symptoms can also affect more than one part of the body. In some cases, individuals may seem typical in early childhood but develop symptoms during adolescence or adulthood. 

Effect on Children

Intellectual disability is the most common developmental disability. Approximately 439,000 affected children and youth ages 3 to 21 received support under the Individuals with Disabilities Education Act (IDEA) in 2019. However, the number of affected children could be higher because data were unavailable for some states.

Children with disabilities may experience issues with communicating, socializing with their peers, or taking care of their personal needs. The child may develop more slowly than others their age, taking longer to walk, feed themselves, get dressed, and handle other daily functions. Some children may always require assistance with these activities.

Effect on Adults

The United States and other industrialized nations are seeing an increase in the longevity of adults with intellectual disabilities. For these people, aging can bring progressive health risks stemming from early age-onset conditions. They also face discrimination and exclusion, which trigger secondary mental health disorders, such as anxiety and depression. Nevertheless, many adults with mild intellectual disabilities can thrive on their own or with minimal support.

Causes

ID can be caused by a variety of factors, including injury, disease, or an issue with brain development. Chromosomal defects such as variants and inborn errors of metabolism can permanently alter cognitive function. Intellectual disabilities arise from such factors as:

• Down syndrome, the most common cause of ID in the United States
• Fragile X syndrome, the most commonly known congenital (present at birth) cause of ID
• Dravet syndrome, a rare congenital cause of ID
• Huntington's disease, a hereditary cause of late-onset ID

Intellectual and developmental disabilities also stem from cognitive disruption due to:

• Brain malformations
• Prenatal alcohol or toxin exposure
• Prenatal nutritional deficiencies
• Maternal infections or complications leading to brain injury
• Pre- or postnatal brain infections
  

Diagnosing Intellectual Disability

Pediatricians and other child healthcare providers can screen for IDDs at your well-child visits and annual exams. You might complete a brief, standardized test that your pediatrician will score. A medical professional may interview you and observe your child for symptoms as well.

Gold-standard tests for intellectual disability include the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview, Revised. In some cases, a chromosomal microarray analysis (CMA) or the array comparative genomic hybridization (aCGH) test is used to pinpoint genetic mutations.

Evaluating Intellectual and Adaptive Functioning

Overall, intellectual disability is identified by problems in both intellectual and adaptive functioning, as such:

• Intellectual functioning: According to the American Psychiatric Association, intellectual functioning entails “reasoning, problem-solving, planning, abstract thinking, judgment, academic learning, and learning from experience." 

Measuring Intellectual Functioning

Intellectual functioning is measured by a standardized exam that can determine IQ score. An IQ test score between 70 and 75 indicates that the individual experiences limitations in intellectual functioning.

• Adaptive functioning: This has to do with skills your child needs to live safely and responsibly. To evaluate functioning, clinicians assess behaviors via questionnaires or observations of the patient’s performance of a skill.

Measuring Adaptive Functioning

Adaptive functioning is measured in these three areas:

• Conceptual: This includes reading, math, writing, knowledge, and memory.
• Social: This encompasses social skills, communications, the ability to follow rules, and making and keeping friends.
• Practical: This includes living independently, taking care of personal hygiene, and being able to hold down a job, manage money, and handle organizational tasks.

Evaluating Severity

The AAIDD uses the Supports Intensity Scale (SIS) to assess the severity of ID. It focuses on the types of supports an individual requires to thrive, not just the limitations of the mentally challenged, and ranks them as follows:

• Mild to moderate ID: Most individuals with ID have mild disabilities. They tend to be slower in cognition and daily living skills, but they can learn to function with minimal assistance. Those with moderate ID can travel to familiar places and use basic life skills with a little more help.
• Severe ID: Severe intellectual disability symptoms include major developmental delays and limited communication skills. Individuals may be able to care for themselves and learn simple daily routines. However, they need supervision in social settings and family or institutional care.
• Profound ID: People with profound ID typically have congenital syndromes. They cannot live on their own and require close attention and assistance with self-care. These individuals often have accompanying medical issues and physical limitations.
  

Related Conditions

Intellectual disability frequently co-occurs with other developmental, physical, medical, and psychiatric conditions. It can be challenging to identify these illnesses if the affected person has limited communication skills. Commonly related conditions include:

• Anxiety and depression disorders
• Autism spectrum disorder
• Defects of the heart, eyes, digestive tract, and other organs
• Epilepsy (neurological disorder affecting brain activity that causes seizures)
• Impulse control disorder
  

Getting Involved as a Parent

It may take some time to accept your child’s diagnosis. As you come to terms with it and get to know your child, though, you will learn how to communicate and respond to their needs. Your pediatrician can also guide you in caring and advocating for your child's well-being.

Tips for Helping Your Child at Home

These tips can help your child develop skills at home:

• Encourage your child with mild to moderate ID to be responsible and independent.
• Give them chores and help them learn everyday self-care skills as they are able.
• Read to your child and enjoy fun activities with them and your other family members.

Your local school can be your partner in caring for your child with ID. Federal laws provide for special education and accommodations in public schools. You can ask for an evaluation to determine your child’s needs and help develop an Individualized Education Program (IEP) for a successful learning journey.

Summary

Intellectual disability is characterized by impediments in intellectual and adaptive functioning. Symptoms typically show up during childhood, although some manifest later in life. Causes include genetic defects, prenatal or postnatal illness, trauma, and poor maternal or postnatal nutrition.

Most affected people have mild ID, but disorders can also be moderate, severe, or profound. With early detection and intervention, you can connect with specialized services to enhance the well-being of your loved one living with ID.

A Word From Verywell

There are no set rules or trajectories for children with intellectual disabilities. Your child may learn and grow differently or slower than others. You’ll find, though, that they are quite intelligent in their own unique way. Take care of yourself and call on the vast resources available for encouragement and assistance.

It’s an unexpected journey, but you have an abundance of information and support to make it easier and fulfilling.

Frequently Asked Questions

• Can children grow out of a mild intellectual disability?

  Intellectual disabilities are generally lifelong. However, early diagnosis, treatment, and support might minimize symptoms and enable your child to function well into adulthood.

• How do you know if your child is intellectually disabled?

  How an intellectual disability presents itself depends on the underlying cause and severity. Profound or severe cases are usually evident soon after birth. With milder forms, intellectual disability symptoms may include:

  • Not meeting developmental milestones, such as sitting, crawling, or walking later than most children
  • Difficulty speaking clearly or at all
  • Learning difficulties at school

  If you suspect that your child has an intellectual disability, talk with your child’s healthcare provider. They can get you in touch with a developmental pediatrician. Reach out to a public school or an early intervention program for information and support.

• What are the differences between intellectual and developmental disabilities?

  Intellectual disability is a type of developmental disability (DD). The Centers for Disease Control and Prevention (CDC) describes DD as a broader category of “conditions due to an impairment in physical, learning, language, or behavior areas.” “IDD” describes situations in which intellectual disability and other disabilities co-occur.

  Examples of intellectual and developmental disabilities include:

  • ADHD
  • Autism spectrum disorder
  • Cerebral palsy
  • Hearing loss
  • Vision impairment
  • Spina bifida

What are some intellectual and developmental disabilities?

What are the most common intellectual disabilities?

What are the most common types of developmental disabilities?

What are the 4 subtypes of intellectual disability?