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Intellectual Disability

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

  • Cognitive functioning, such as learning, problem solving, 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.

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Expert Q&A: Intellectual Disability

These terms are not the same, though there is some overlap. Developmental disability is a broad category that includes intellectual disability (ID) as well as autism spectrum disorder and other developmental diagnoses. Intellectual disability refers to people whose cognitive ability and adaptive functioning are significantly below average. People with autism spectrum disorder have difficulties with social interaction and impairments in communication; many also have intellectual disability.

Parents and caretakers are often the first to notice delays in a child’s development.

If you’re concerned about the development of your infant or toddler, or you suspect your child has a disability, talk with your child’s pediatrician. You may also contact your local early Intervention program directly (see links below) and ask to have your child evaluated. Early intervention is a national system of services that helps babies and toddlers (birth to three years) with developmental delays or disabilities. Evaluation is provided free of charge.

See contact information for state early intervention programs. Learn more about early intervention from the Center for Parent Information and Resources.

Intellectual disability involves problems in both intellectual and adaptive functioning.

Intellectual functioning is assessed with an exam by a doctor and through standardized testing. While a specific full-scale IQ test score is no longer required for diagnosis, standardized testing is used as part of diagnosing intellectual disability. A full scale IQ score of around 70 to 75 indicates a significant limitation in intellectual functioning. However, the IQ score must be considered in relation to the bigger picture of the person’s general mental abilities. Also, specific areas of intellectual functioning (identified in IQ subtest scores) can vary a great deal. So the full scale IQ score may not accurately reflect overall intellectual functioning.

Adaptive functioning refers to a child’s abilities with common skills needed for everyday life compared to other children the same age. Three areas of adaptive functioning are considered: conceptual (such as language and academic skills); social (such as communication skills and the ability to follow rules); and practical (such as personal care and other daily life skills). Adaptive functioning is assessed through standardized measures (questionnaires/checklists) with the individual and through interviews with family members, teachers and caregivers.

While it is possible that he is experiencing depression, the first step is to consider and look for any possible medical cause for his change in mood and/or behavior. Work with your health care provider to have a full physical exam and appropriate laboratory tests. At times, behaviors can provide clues to medical illness, such as head banging that indicates a headache, or tugging at an ear that indicates an ear infection. It is important to resist the temptation to reach a premature conclusion.

On the other hand, it is important not to overlook symptoms that may indicate depression or another mental health condition just because a person has an intellectual disability. If medical illness has been ruled out, seek an evaluation from a mental health professional – if possible, one with experience working with individuals with intellectual disability.

Theoretically these types of treatment are appropriate to consider and can be important components of a comprehensive treatment plan. However, keep in mind that a diagnosis of intellectual disability implies deficits in cognitive ability that can interfere with the ability to make use of therapy.

There is nothing about intellectual disability that necessarily disqualifies a person from enjoying all of the rights afforded to all other citizens. There are additional protections for people with disabilities, including intellectual disabilities, such as laws and regulations that mandate reporting of certain types of perceived abuse. These can vary in different locations and jurisdictions.

A diagnosis of intellectual disability is a step in determining whether a person is eligible to receive various services and supports, and to ensure rights are protected, including:

  • Special education services.
  • Home and community-based Medicaid waiver services.
  • Social Security Administration benefits.
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Rubí E. Luna, M.D.

UCLA Semel Institute for Neuroscience and Human Behavior
Child and Adolescent Psychiatry Fellow, PGY-5

Medical leadership for mind, brain and body.

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