A cognitive issue.
Mental retardation has different levels. There is Mild intellectual disability; moderate intellectual disability; severe intellectual disability; and Profound intellectual disability.https://www.floridahospital.com/mental-retardation-mr/symptoms-and-signs-mental-retardation
Mildly retarded people can live alone if necessary and often get married. Profoundly retarded people need caring in their whole life.
The old and still popular terms were adjusted downward from normal- Moron ( high and low grade) Imbecile, and Idiot. for some reason Moron and Idiot remain in popular usage but imbecile, even in slang usage is rarely used.
Mental retardation occurs in 70-90% of persons with infantile spasms, usually involving severe to profound retardation. Other neurological deficits, such as cerebral palsy, may be seen in about 30-50% of patients.
There is no evidence to suggest that Walt Whitman had any form of mental retardation. He was a celebrated American poet known for his profound work, particularly in free verse poetry.
It is more accurate.
Overstudy does not cause mental retardation.
TThere are quite high as it comes in different types of mental retardation.
Affected children with Hurler syndrome lose previously attained skills (milestones) and eventually suffer from profound mental retardation
Exposure to lead can also cause mental retardation.
literature review on mental retardation with reference
The term idiot is now offensive. It has referred to a person of profound retardation unable to learn proper speech or guard against common dangers. Generally having a mental age of less than three and an intelligent quotient of under 25. Clumsy is awkward in motion or action and can be expected of a person of profound retardation