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. " 

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.

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:

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.

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.

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.

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.

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.

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.

Not meeting developmental milestones, such as sitting, crawling, or walking later than most childrenDifficulty speaking clearly or at allLearning 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.

Examples of intellectual and developmental disabilities include:

ADHDAutism spectrum disorderCerebral palsyHearing lossVision impairmentSpina bifida