Short answers, pulled from the story.
Intellectual disability is defined as a dual deficit involving an intelligence quotient below 70 combined with significant limitations in adaptive behaviors required for daily living. This neurodevelopmental disorder must be confirmed through clinical evaluation and individualized standard IQ testing to distinguish it from cultural differences or lack of opportunity.
Down syndrome is the most common genetic cause of intellectual disability, resulting from an extra copy of chromosome 21. Other genetic causes include Fragile X syndrome, Trisomy 18, Phelan-McDermid syndrome, and rare chromosomal abnormalities such as 49, XXXXY syndrome.
In 2010, a legal shift in the United States erased the word retardation from federal law and replaced it with intellectual disability. This change did not alter the human reality of the condition but updated the terminology used in federal statutes.
The average lifetime cost of a person with intellectual disability in the United States is $223,000 in 2003 US dollars for direct costs and $771,000 for indirect costs. The total direct and indirect costs amount to slightly more than a million dollars per person, which is double the cost associated with serious vision or hearing impairments.
The eugenics movement of the early 20th century led to forced sterilization and prohibition of marriage in most developed nations. Adolf Hitler later used this ideology as a rationale for the mass murder of people with intellectual disability during the Holocaust.
Intellectual disability affects approximately 2 to 3 percent of the global population, meaning roughly 95 million people live with some form of the condition. The majority of these individuals, between 75 and 90 percent, possess what is classified as mild intellectual disability.