Intellectual disability: An inability to cope with the real world (not an inability to cope with IQ tests)

There is an agreed international definition of ID (ICD-11, DSM-V, AAIDD):
• Significantly low intellectual ability (usually taken as IQ 70 or 75).
• Significantly low level of adaptive/social behaviour (often defined as two Standard Deviations below the population mean in the composite measure of in two sub scales).
• All occurring before the age of 18 years.

But there are some problems with this definition.
• It is a condition largely created by definition, with arbitrary IQ and adaptive behaviour cut off scores.
• It appears to be the only condition in DSM-V based on test scores.
• The tests of IQ and adaptive behaviour are not accurate in low range even when used on the population for which they were standardized. This can lead to misdiagnosis.
• The question as to what IQ tests mean when used on groups for which the test was not standardized, has not been adequately address. We do know that different populations have different mean IQs but we don’t know why this is, or what the test results predict, or mean.

We need to move to definitions based far more on clinical judgment and less on test scores. For example: An inability to cope with the intellectual demands of ones environment.