Intellectual Disabilities
Basic Information

Intellectual Disabilities

The term "intellectual disability" is a specific type of disability. It is caused by limited mental capacity. Limited mental capacity makes it difficult to develop important mental abilities. This includes reasoning, planning, thinking, and judgment. This limited mental capacity makes it difficult to learn new things. The ability to learn is a very important mental ability. We learn new information and skills in school. We learn from our past mistakes. We learn how to do many things by watching others. When this ability to learn is lacking, it causes many problems in everyday life.

The Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Association (APA, 2013) lists three main criteria for intellectual disabilities:

1. Significant limitations in intellectual functioning (mental abilities);
2. Significant limitations in adaptive functioning (conceptual skills, social skills, and practical life skills);
3. T...

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What are intellectual disabilities?

  • An intellectual disability (formerly mental retardation) is a type of disability that results from limited mental capacity.
  • Limited mental capacity makes it difficult to develop important mental abilities including reasoning, planning, thinking, and judgment, and makes it difficult to learn new things.
  • There are three main criteria for intellectual disabilities (IDs):
    • Significant limitations in intellectual functioning (mental abilities);
    • Significant limitations in adaptive functioning (conceptual skills, social skills, and practical life skills);
    • The problems begin before age 18
  • Some medical conditions that can cause ID are associated with obvious physical features and are so noticeable that they are easily identified at birth.
  • Another early sign of an intellectual disability is developmental delay where children with ID sit, walk, and talk later than other children do.
  • A related issue is the slower development of social skills, which becomes evident when children play together as individuals with ID struggle to understand and follow social rules and customs.

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What types of learning are affected by intellectual disabilities?

  • Intellectual disabilities affect three different types of learning, including academic learning, experiential learning, and social learning.
  • Experiential learning occurs through cause and effect. For example, suppose a child touches a hot stove. This experience causes the child to learn to avoid touching a stove. However, a child with an ID does not learn from this painful experience and does not understand the stove (the cause) caused the painful burn (the effect).
  • Social learning occurs by watching other people in social situations. For example, we might notice it is normal to greet people by shaking hands or offering a hug.
  • Social learning allows us to learn social skills that are needed to get along well with other people and that are critical to life success.
  • Academic learning happens through formal education and includes the skills of reading, writing, and math.

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How common are intellectual disabilities and do they affect life expectancy?

  • An estimated 7 to 8 million Americans have an intellectual disability, which means that about 1 in 10 families in the United States are affected by an intellectual disability.
  • As a group, people with intellectual disabilities have a shorter life expectancy than the general population.
  • However, it really depends on the underlying cause of the disability and some people with intellectual disabilities are at greater risk than others of premature death.
  • The life expectancy for people with intellectual disabilities has dramatically improved over the past few decades. For example, 20 years ago, people with Down syndrome were not expected to live past age 35, but today, these same people would live to 55 years of age.

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What are the causes of intellectual disabilities?

  • Intellectual disabilities have many causes - some are preventable and others are not.
  • These causes can be grouped into four categories:
  • Four conditions that are the most common causes of ID are:
  • Medical Causes - Pre- and post-natal exposure to alcohol, drugs, toxins, and certain infections can have a devastating effect on brain development and can result in physical and mental defects, and even death of an infant.
  • Several types of brain damage including Traumatic Brain Injury (TBI), congenital brain damage, and progressive brain damage can lead to intellectual disabilities.

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How are intellectual disabilities diagnosed?

  • The first indication of an intellectual disability is usually a child's physical and behavioral characteristics.
  • Once an intellectual disability is suspected, a formal evaluation and assessment begins.
  • The evaluation begins with a complete physical examination. A thorough review of medical history identifies any physical or medical causes of the troubling symptoms.
  • A thorough assessment usually includes the following:
    • comprehensive medical exam;
    • possible genetic and neurological testing;
    • social and familial history;
    • educational history;
    • psychological testing to assess intellectual functioning;
    • testing of adaptive functioning;
    • interviews with primary caregivers;
    • interviews with teachers;
    • social and behavioral observations of the child in natural environments

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Are there different severity levels of intellectual disabilities?

  • The DSM-5, provided by the American Psychiatric Association, has severity codes that indicate the diagnosing clinician's impression of the severity of adaptive functioning.
  • Severity is assessed across three domains, which are conceptual, social, and practical life skills.
  • Mild intellectual disability includes about 85% of people with intellectual disabilities. In many cases, people in this category can live independently within their communities with a minimal level of additional supports.
  • Moderate intellectual disability includes around 10% of the individuals with intellectual disabilities and people in this range have adequate communication skills but complexity is more limited. Most self-care activities can be performed but may require extended instruction and support and independent employment can be achieved in positions that require limited conceptual or social skills. Independent living may be achieved with moderate supports such as those available in group homes.
  • Severe intellectual disability describes 3 to 4% of this population and communication skills are very basic. Self-care activities require daily assistance and residence in supported housing is usually necessary.
  • Profound intellectual disability describes a very small portion of the persons with intellectual disabilities. Only 1 to 2% fall into this category and people in this category are dependent upon others for all aspects of daily care.
  • The American Association on Intellectual and Developmental Disabilities (AAIDD) also has a category system for classifying severity.
  • This system evaluates a person's strengths and abilities, not just their limitations, and categorizes each person's level of functioning based on the level of support that person needs to function reasonably well in his or her preferred environment.
  • Intermittent support: Those in this category usually only require additional supports during times of transition, uncertainty, or stress. This level of support would be categorized under the APA standards as mild intellectual disability.
  • Limited support: With additional training, those in this category can increase their conceptual skills, social skills, and practical skills. They may still require additional support to navigate everyday situations. People in this group would often be categorized by APA standards as moderate intellectual disability.
  • Extensive support: These individuals have some basic communication skills and can complete some self-care tasks, but will usually require daily support. This level of support is usually associated with severe intellectual disability by APA criteria.
  • Pervasive support: Pervasive support describes the most intense level of support and daily interventions are necessary to help the individual function. This classification is associated with those who have profound intellectual disability.

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What types of therapies can be helpful or not helpful for people with intellectual disabilities?

  • Various therapeutic services can improve a person's adaptive behavioral skills and these therapies are helpful for many people with intellectual disabilities.
  • Occupational therapy can teach meaningful and purposeful activities; Self-care (e.g., grooming, dressing, feeding, bathing); Employment activities and skills; Leisure activities (e.g., knitting, playing games); and Domestic activities (e.g., cooking, cleaning, laundry).
  • Speech therapy can improve communication skills, receptive and expressive language skills, speech articulation, and vocabulary.
  • Physical therapy enhances quality of life by maximizing mobility and providing adaptive solutions to mobility problems, and increasing sensory integration.
  • There are no reliable research studies to support claims of effectiveness of the following types of therapy:
    • Orthomolecular therapy claims vitamins and minerals can treat, or reverse a number of different conditions including intellectual disabilities, but diet and nutritional supplements have not been proven to enhance cognitive functioning, performance, or learning in individuals with intellectual disabilities.
    • Medications - currently, no medication can treat the entire spectrum of disorders that cause intellectual disabilities. Medications are legitimately prescribed when neurocognitive disorders are the root cause of the disability.
    • Talk therapy, which refers to psychotherapy, is useful for many psychiatric disorders. However, psychotherapy cannot treat, stop, or cure disabilities. Such therapies rely on a person's cognitive, emotional, and verbal abilities in order to promote change and as a result, people with intellectual disabilities are not good candidates for such therapies.
    • Genetic manipulations: Someday it may be possible to use genetic manipulations to correct the genetic causes of some intellectual disabilities, but at this time, it is not possible.

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Basic Information
Introduction to Intellectual DisabilitiesCauses of Intellectual DisabilitiesDiagnosis of Intellectual DisabilitiesHistorical & Contemporary Perspectives of Intellectual DisabilitiesIntellectual Disabilities & Supportive RehabilitationSupport for Families of People with Intellectual DisabilitiesIntellectual Disabilities Summary & ConclusionIntellectual Disabilities Resources & References
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Childhood Mental Disorders and Illnesses

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