What is ID?
Intellectual Disability (ID) is a term used to describe a wide range of disorders. Many of these disorders have a genetic, medical, biological or psycho-social cause. The term 'Learning Disability' is still used in the UK. Sometimes the diagnosis of an ID is further specified as being 'Mild', 'Moderate' or 'Severe' - this is often based upon level of cognitive disability, i.e. IQ score. Although there are many hundred of different disorders, they share 3 common factors:
- Cognitive processing difficulties (difficulties with problem-solving, with planning, with abstract thinking, with reasoning skills, and they will have an IQ score of less than 70 ± 5)
- Adaptive functioning difficulties (difficulties with self-care, with domestic skills, with social skills or communication problems)
- These problems manifest before the age of 18 years old.
How many people?
That is a hard question to answer. Most countries do not keep an accurate register of the number of people with an ID. There have been a number of studies attempting to answer this very question. The consensus currently is that approximately 2% of the world's population have an ID. However, this is merely an estimate, and currently we simply do not know the true number of people who have an ID.
Visit the RESOURCES page to find links to the studies that have estimated the number of people with an ID.
Diagnosing?
Our understanding of ID has changed over the last few decades and so too has the way in which we diagnose IDs. In the past a person was often diagnosed as having an ID on the basis of their IQ score alone. Now days, a person's functional ability has a greater role in the diagnostic process.
The two main systems for arriving at a diagnosis are the American Psychiatric Association's DSM-V, and the World Health Organisation's ICD-11.