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 standard deviation of 15. The range is called borderline because it is on the borderline of the criteria for diagnosis of intellectual disabilities (historically referred to as mental retardation
) in the Diagnostic and Statistical Manual of Mental Disorders
Consistent scores within the 70 to 75 range are considered suggestive of borderline intellectual functioning and may indicate a mental disability. However, it is recommended that multiple test instruments be administered to confirm a diagnosis. No diagnosis should be made on the basis of a single test.