What to know about intellectual disability

Intellectual disability occurs when a person has difficulty with general mental abilities. This may impact their:

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• intellectual functioning, such as their learning, judgment, problem solving, abstract thinking, memory, reasoning, and academic skills
• practical functioning, which refers to the ability to function and take care of oneself independently, such as performing personal care tasks, managing money, and performing work, school, or home tasks
• social functioning, which refers to the ability to function normally in society by using skills such as social judgment, communication, understanding and following social rules and cues, understanding the consequences of one’s actions, and making friends

According to the American Psychiatric Association, 1% of the population have intellectual disability. Around 85% of these people have mild cases.

In the United States, intellectual disability affects around 1 in 10 families.

Males are more likely to receive a diagnosis of intellectual disability.

In many cases, the precise cause of intellectual disability is unknown. Typically, however, the condition develops due to injury, disease, or certain brain conditions.

Any condition that impacts the brain and begins before the age of 18 years, even before birth, can cause intellectual disability. However, intellectual disability can also develop later in childhood or adolescence due to conditions that cause brain damage.

Some common causes of intellectual disability include:

• certain genetic conditions, such as Down syndrome, phenylketonuria, or fragile X syndrome
• fetal alcohol syndrome
• congenital anomalies or brain malformations
• some infections, such as meningitis, measles, or whooping cough
• exposure to toxins such as mercury or lead
• serious head injury
• stroke
• maternal disease, such as rubella, drug use, or infection during pregnancy
• problems at birth, such as insufficient oxygenation
• extreme malnutrition
• insufficient medical care

People with more severe forms of intellectual disability usually experience more severe symptoms that are noticeable at a young age.

There are a variety of signs and symptoms that a person with intellectual disability might experience. Generally, people with this condition tend to take longer to learn and develop intellectually than other people.

They also tend to have difficulty with adaptive behaviors. Adaptive behaviors are the conceptual, social, and practical skills that people learn and use in everyday life to function.

Some common symptoms of intellectual disability include:

• reaching developmental milestones — such as sitting up, crawling, walking, or talking — later than other children
• difficulty speaking or reading
• difficulty understanding or following social rules or cues
• difficulty understanding the results or consequences of their actions
• difficulty solving problems, thinking logically, or thinking abstractly
• difficulty planning or following schedules or routines
• difficulty remembering things
• difficulty letting others know their needs
• difficulty understanding systems such as the need to pay for things, time, or how to use a phone
• difficulty with social skills
• a reduced ability to perform regular personal care, such as eating, getting dressed, or completing household tasks
• limited functioning in one or more daily activities
• reduced judgment and decision making skills
• difficulty learning from experience
• communicating using nonverbal means, such as expressions and gestures
• difficulty regulating emotions and behaviors

In most cases, the symptoms of intellectual disability start in early childhood or adolescence. In particular, difficulty with language and motor skills may occur by the age of 2 years.

People with mild intellectual disability may not show any obvious signs until they begin to have difficulty with schoolwork.

To diagnose intellectual disability, a doctor will perform several tests to assess the person’s intellectual and adaptive functioning.

These tests may include:

• an IQ test (a score of 70–75 may indicate intellectual disability)
• interviews with the individual and others who have observed their adaptive functioning — that is, their conceptual, social, and practical functioning — such as family members or teachers
• whether or not someone has the skills necessary to live independently
• general medical tests
• neurological tests
• psychological tests
• special education tests
• hearing, speech, and vision tests
• physical therapy evaluations

Intellectual disability tends to develop and cause noticeable symptoms before the age of 18 years.

Intellectual disability is a lifelong condition.

Although there is currently no cure, most people can learn to improve their functioning over time. Receiving early, ongoing interventions can often improve functioning, thereby allowing someone to thrive.

Most treatment plans for intellectual disability focus on the person’s:

• strengths
• needs
• support needed to function
• additional conditions

Many services exist to help people with intellectual disability and their families get the support they need. Most of these services allow someone with intellectual disability to function normally in society.

Someone’s diagnosis typically determines which services and protection of rights, such as special education or home or community services, they are eligible to receive under federal or national law. It also usually helps determine which supportive services they may need.

Supportive services include:

• early interventions that work to identify intellectual disability in infants and toddlers
• special education and academic support, such as individual education plans, which are available in the U.S. under federal law for free to every child with intellectual disability
• transition services that help people with intellectual disability transition to adulthood after high school
• day programs
• vocational programs, such as job coaching or skill learning
• housing options
• case managers to help coordinate services and ensure that the individual receives proper care
• psychological or psychiatric services
• speech and language pathology or audiology services
• therapeutic recreation
• rehabilitation counseling
• adapted equipment or assistive technology

Family members, caregivers, friends, co-workers, and community members can also provide additional support to people with intellectual disability.

With proper support and treatment, most people with intellectual disability are capable of achieving successful, production roles in their communities.

However, how well someone is able to cope and function with intellectual disability is also dependent on the severity of their condition and any other underlying genetic or medical conditions they have.

Parents and caregivers who think that their child may have intellectual disability should talk with their child’s doctor or nurse as soon as possible. Receiving early, ongoing intervention is very important in ensuring that someone with this condition can reach their full potential.

If the doctor suspects intellectual disability or the child continues to experience symptoms, they should visit a pediatrician who specializes in diagnosing developmental conditions.

To find local specialists, click here.

Other tips for parents and caregivers include the following:

• Learn the specifics about the child’s intellectual disability, including their limitations, strengths, needs, and other individual factors.
• Connect with other parents who have children with intellectual disability.
• Encourage activities that support independence and responsibility, such as chores, dressing, feeding, or bathing.
• Seek support from community, medical, or other supportive services.
• Be patient, kind, hopeful, and understanding.
• Get involved with social, recreation, sports, or other activities.
• Try to avoid negative thinking, projections, or words.
• Work with early intervention services to develop an Individualized Family Services Plan that focuses on the child’s and family’s needs.
• Contact local school systems or elementary schools to get access to special education and related services.
• Practice social and communication skills.
• Recognize that parents and caregivers can help improve the functioning of someone with intellectual disability.
• Be as clear as possible, using demonstrations such as a picture or hands-on materials rather than verbal directions.
• Break longer and new tasks into simpler steps.
• Work with teachers and academic support workers to assess the child’s progress at school and at home.
• Work with adolescent or child psychiatrists to set appropriate expectations for the individual.

People with intellectual disability have varying limits to their ability to learn and function in society, and they often learn slower than others.

However, receiving early, ongoing treatment in the form of supportive services can often help people with intellectual disability function normally or independently.

Contact a doctor as soon as possible if a child has any signs or symptoms of intellectual disability.