Borderline Intellectual Functioning Overview

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In the Diagnostic and Statistical Manual of Mental Disorders version 4 (DSM-IV), there was a diagnostic category called "mental retardation." In 2013, when the new DSM-5 came out, mental retardation had disappeared; in its place was a new disorder called "intellectual development disorder." 

People with "mental retardation" were diagnosed using DSM-IV, and the diagnosis was made largely through standardized IQ tests. If IQ scores came out below 70, the individual was considered to have an intellectual disability.

People with "intellectual development disorder" are diagnosed using DSM-5, and while IQ scores still play an important role, other issues are considered. According to the Intellectual Disability Fact Sheet from the American Psychiatric Association (which publishes the DSM):

Borderline Intellectual Functioning

Borderline intellectual functioning refers to estimated intelligence quotient scores within the 70 to 75 range on an intelligence test with an average of 100 and a standard deviation of 15. The range is called borderline because it is on the borderline of the criteria for the diagnosis of intellectual disabilities (historically referred to as mental retardation) in the Diagnostic and Statistical Manual of Mental Disorders (DSM).

Consistent scores within the 70 to 75 range are considered suggestive of borderline intellectual functioning and may indicate a mental disability.

No diagnosis should be made on the basis of a single test. Multiple test instruments should be administered to confirm a diagnosis.

Receiving State or Federal Services

In the past, because of the weight given to IQ scores alone, people with scores between 70 and 75 were generally denied services and supports provided to people with scores below 70. Today, however, there is more of an emphasis on individuals' ability to function and manage daily living skills. Thus, if an individual has a borderline intellectual disability, he may or may not receive services. The determination will depend on upon a number of factors; for example:

  • What other diagnosis goes along with borderline intellectual disability? For example, an individual with autism and an IQ of 75 may have significantly more difficulty with daily life activities than an individual with Down syndrome and the same IQ.
  • Where does the individual live? Rules regarding agency services vary from state to state.
  • What kinds of supports are available to an individual in his living situation?
  • Does this individual have physical challenges that make it difficult for him to perform ordinary life skills? Some genetic disorders which cause lowered IQ can also cause lowered muscle tone, poor coordination, and other issues.
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