Intellectual impairment, also known as mental or cognitive impairment, is cognitive functioning that is below normal and which impacts everyday life. The internationally accepted definition according to the American Association on Intellectual & Developmental Disabilities (AAIDD) is that intellectual impairment is demonstrated when a person's intellectual function and the ability to adapt is shown to have dramatic limitations, as demonstrated by their social and practical skills. The impairment must also originate before the age of 18. Cognitive impairment typically means that a person needs adjustments in educational approaches, and in some cases, assistance in living. It does not necessarily mean a person cannot be a positive contributor to society.
When a person has mental impairment, their capacity for performing mental tasks and problem solving is lower than average. At the very least, this usually means the individual needs some additional time to complete what he is doing. In the worst case, it means the individual becomes completely dependent on other individuals and needs supervision throughout the entire day. Thus, a broad range of intellectual impairment exists.
Intellectual impairment is divided into four basic categories that describe the level of impairment. These include mild, moderate, severe and profound. A classification of mild means the individual has an intellectual quotient (IQ) between 51 and 70. Moderate mental impairment means an IQ of 36 to 50. Experts give a designation of severe impairment when an IQ is 21 to 35. With an IQ of 20 or less, an individual is severely impaired.
People who are intellectually impaired exhibit symptoms such as disorganization in learning and understanding abstract constructs. The ability to learn is necessary to adapt and change, so another symptom is problems with adaptive skills. Examples of adaptive skill areas include social interaction, work and health and safety.
Intellectual impairment is not always considered a disability, but it can be. In this instance, it might be covered by anti-discrimination laws present in the country in which the person lives. For example, in the United States, intellectual impairment is covered by the Americans With Disabilities Act (ADA). This law considers intellectual impairment a disability if a) the impairment limits one or more major life activities such as caring for oneself or working, b) the intellectual impairment combined with another impairment limits one or more major life activities, c) the individual has a history of substantial intellectual impairment or d) no mental impairment is present but others treat the individual as if it is.
Doctors and scientists believe some cases of intellectual impairment are purely genetic in origin. Other cases are related to controllable factors such as maternal drug use — including some prescription medications — that causes problems in fetal brain development. Cases of brain injury also can cause issues with mental functioning, but because brain injury and subsequent cognitive problems don't always result prior to age 18, not all of these cases technically can be classed as an intellectual impairment according to the definition set by AAIDD.