Understanding Intellectual Impairments


Intelligence is the general mental capacity that involves reasoning, planning, solving problems, thinking abstractly, comprehending complex ideas, learning efficiently, and learning from experience (AAIDD, 2010).

Historically, intellectual disability (previously termed mental retardation) has been defined by significant cognitive deficits—which have been established through a standardized measure of intelligence, in particular, with an IQ score of below 70 (two standard deviations below the mean of 100 in the population)—and also by significant deficits in functional and adaptive skills.

Adaptive skills involve the ability to carry out age-appropriate daily life activities

Intellectual disability involves problems with general mental abilities that affect functioning in two areas:

Intellectual functioning (such as learning, problem solving, judgement).

Adaptive functioning (activities of daily life such as communication and independent living).

Intellectual disability affects about 1% of the population, and of those about 85% have mild intellectual disability. Males are more likely than females to be diagnosed with intellectual disability.

Intellectual functioning is measured with individually administered and psychometrically valid, comprehensive, culturally appropriate, psychometrically sound tests of intelligence.

While a specific full-scale IQ test score is no longer required for diagnosis, standardized testing is used as part of diagnosing the condition.

A full-scale IQ score of around 70 to 75 indicates a significant limitation in intellectual functioning. However, the IQ score must be interpreted in the context of the person’s difficulties in general mental abilities.

Moreover, scores on subtests can vary considerably so the full-scale IQ score may not accurately reflect overall intellectual functioning. Therefore, clinical judgment is needed in interpreting the results of IQ tests.

Persons with profound intellectual disability often have congenital syndromes (Sattler, 2002). These individuals cannot live independently, and they require close supervision and help with self-care activities.

They have very limited ability to communicate and often have physical limitations.

Individuals with mild to moderate disability are less likely to have associated medical conditions than those with severe or profound ID.

The majority of people with ID are classified as having mild intellectual disabilities. Individuals with mild ID are slower in all areas of conceptual development and social and daily living skills.

These individuals can learn practical life skills, which allows them to function in ordinary life with minimal levels of support.

Individuals with moderate ID can take care of themselves, travel to familiar places in their community, and learn basic skills related to safety and health. Their self-care requires moderate support.

Adults with ID should be encouraged to develop routines that involve more stimulating pursuits, such as regular exercise or opportunities to interact with others.



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