Summary and Description
What is Intellectual Disability?
What is intellectual functioning?
What is adaptive behavior?
(a) Diagnosing intellectual functions:
Intellectual functions are typically assessed with an intelligence quotient (IQ) test. IQ tests are standardized assessments that assess a person's intelligence. Regarding the intellectual functions criteria, the DSM-V (2013) indicates criteria for this area has been met if they score two standard deviations or more below the population average, including a margin of measurement error.
(b) Diagnosing adaptive functioning:
Adaptive functioning is composed of three different domains: conceptual, social, and practical (DSM-V, 2013). This criteria is met when at least one of these domains is impaired and needs continuous support (DSM-V, 2013). This area is typically assessed using clinical evaluation and individualized measures (DSM-V, 2013).
The onset of the above deficits occurs during the developmental period, which is before the age of 18 (DSM-V, 2013).
- IQ 50 to 70
- Slower than typical in all developmental areas
- No unusual physical characteristics
- Able to learn practical life skills
- Attains reading and math skills up to grade levels 3 to 6
- Able to blend in socially
- Functions in daily life
This includes about 85% of people with ID (Gluck, 2014). Those with mild ID had read but most likely have difficulty with reading comprehension (Gluck, 2014). A person with mild ID may achieve academic success.
- IQ 35 to 49
- Noticeable developmental delays (i.e. speech, motor skills)
- May have physical signs of impairment (i.e. thick tongue)
- Can communicate in basic, simple ways
- Able to learn basic health and safety skills
- Can complete self-care activities
- Can travel alone to nearby, familiar places
This includes about 10% of people with ID (Gluck, 2014). Those with moderate ID may have adequate communication skills but will struggle to complex communication (Gluck, 2014). For example, a person with moderate ID may struggle with problem solving, decision making, and understanding facial expressions. People with moderate ID can care for themselves, but typically need support (Gluck, 2014).
- IQ 20 to 34
- Considerable delays in development
- Understands speech, but little ability to communicate
- Able to learn daily routines
- May learn very simple self-care
- Needs direct supervision in social situations
This includes 3-4% of people with ID (Gluck, 2014). Those with severe ID can only communicate on a basic level (Gluck, 2014). A majority of people with severe ID are not able to live alone. They are not able to perform self-care activities independently and need supervision (Gluck, 2014).
- IQ less than 20
- Significant developmental delays in all areas
- Obvious physical and congenital abnormalities
- Requires close supervision
- Requires attendant to help in self-care activities
- May respond to physical and social activities
- Not capable of independent living
This includes 1-2% of people with ID (Gluck, 2014). Individuals with severe ID require 24 hour supervision. They depend on others throughout the entire day and have severely limited communication abilities (Gluck, 2014). Finally, individuals with severe ID typically have physical limitations (Gluck, 2014).
Etiology & Contributing Factors
- Genetic conditions such as inheritance, abnormalities of genes, phenylketonuria, and other genetic disorders (The Arc, 2011).
- Problems during pregnancy such as drug and alcohol use as well as illness of the mother during pregnancy (The Arc, 2011).
- Problems at birth such as low birth weight and oxygen deprivation (The Arc, 2011).
- Problems after birth include childhood diseases such as whooping cough, chicken pox, and measles (The Arc, 2011).
- Poverty and cultural deprivation because children growing up in poverty are more likely to be malnourished and often receive inadequate healthcare (The Arc, 2011).
- Developmental delays
- May have physical signs of impairment
- Reading comprehension difficulties
- Difficulties communicating at complex levels
- Difficulty with social cues
- Typically need support in various activities of daily living
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(2015). Intellectual disability. Medline Plus. Retrieved from http://www.nlm.nih.gov/medlineplus/ency/article/001523.htm.
(2015). Intellectual disability. The Arc. Retrieved from http://www.thearc.org/learn-about/intellectual-disability.
(2015). Intellectual disability. WebMD. Retrieved from http://www.webmd.com/children/intellectual-disability-mental-retardation.
Gluck, S. (2014). Mild, moderate, severe intellectual disabilities. Healthy Place. Retrieved from http://www.healthyplace.com/neurodevelopmental-disorders/intellectual-disability/mild-moderate-severe-intellectual-disability-differences/.
Morstad, D. (2012). How prevalent are intellectual and developmental disabilities in the United States? Bethesda Institute. Retrieved from http://bethesdainstitute.org/document.doc?id=413.