Intellectual disability: an inability to cope with an intellectually demanding world

The construct of intellectual disability has developed over centuries and has had different functions at different times; from a concept that was used to describe people from whom society needed protecting from in the late to 19th and early 20th centuries, to one used to describe people who are unable to cope in the current environment. It is now defined in terms of having a measured IQ below a fixed cut off point, usually 70, and a low level of adaptive behaviour also often specified in terms of being below a cut off point. Intellectual Disability demonstrates that neither IQ nor adaptive behaviour can be measured with sufficient accuracy for fixed cut off points to be used and suggests a number of new much more loosely defined constructs of intellectual disability based on clinical judgment.