What is it?
Intellectual disability, ID, is a neurodevelopmental disorder that is characterized by a level of intellectual and adaptive functioning that is well below normal. ID is defined as an IQ below 70 as well as impairments in two or more adaptive behaviors which negatively affects everyday life.
People with ID learn new things slower than average. They often take longer to learn language, and have deficits in memory, social skills, and problem solving abilities.They also often struggle with learning how to take care of themselves.
What causes it?
ID is divided into two categories: syndromic, in which the ID is associated with another medical condition such as Down syndrome, and non-syndromic, in which the ID appears without other associated abnormalities.
Around 30-50% of ID cases are non-syndromic. About a quarter are caused by a genetic disorder, and about 5% are inherited. Malnutrition, exposure to poison, alcohol consumption during pregnancy or other environmental risk factors can also lead a person to develop ID.
What happens during it?
Intelligence is a very hard thing to pin down. Intelligence allows humans to learn, create concepts, understand, recognize patterns, and solve problems. IQ is a controversial measure of these abilities. There is a significant amount of people who argue that IQ is not a good measure of intelligence or is not comprehensive enough, but then again, there are numerous studies that show that IQ is the most reliable predictive factor of school performance as well as success in many other areas of life.
People don’t seem to like it when someone says that there are people who are less intelligent than others – maybe because it seems unfair as our level of intelligence is out of our control. Maybe that’s also why there have been so many attempts to broaden the scope of intelligence to include things like emotional intelligence. Intelligence is, however, just a human abstraction of certain talents, as are other things like the capacity for athletics. The psychological measure known as intelligence wouldn’t be a very useful one if we changed it so that we could eradicate this unfairness by saying that everyone is intelligent in different ways. Some people are intelligent, some people are not. It’s not necessarily fair, but trying to cheat ourselves out of this ethical problem doesn’t help at all – and of course, less intelligent people are just as valuable as human beings as others, not to mention that intelligence is not the only “respectable” and useful trait in humans.
There is no common mechanism that unifies all cases of ID. Most often the capability of processing information in the brain has been impaired. This can be caused by things like impairments in the development of neurons or synapses (the junctions between neurons), or physical damage to the brain due to injury, poison, infection, or lack of oxygen. Intelligence is also somewhat hereditary (although this pattern is by no means obvious), so the genes of two people with below average intelligence, for example, could mix so that their “unintelligence” gets amplified in their child
How can it be treated?
There is no “cure” for ID as it is considered a disability rather than a disease. With good support and teaching, however, many people with ID can be helped to such an extent that they are able to live fulfilling and reasonably independent lives.
There exists a variety of different programs that are designed to help people with ID to learn similar things that are taught at school, obtain jobs, raise their children, and learn basic life skills that many take for granted. The goal is to help them maintain independence and find their place in society. Early intervention can significantly improve the intellectual development of children with ID.
Sources: https://en.wikipedia.org/wiki/Intellectual_disability, http://www.medmerits.com/index.php/article/intellectual_disability/P5, https://en.wikipedia.org/wiki/Human_intelligence