Developmental disabilities is a wide-ranging category of multiple physical and mental impairments, which may include such areas as learning, language, or socialization. According to the Centers for Disease Control and Prevention, about one in six children in the U.S. is known to have one or more developmental disabilities or delays. For the purpose of formal diagnosis, a developmental disability:

  • Appears along the early periods of development but before the age of 22
  • Is typically considered to be present across the lifespan; and
  • Interferes significantly with daily living in at least three areas of self-care, use of language, learning, mobility, independent living, or financial self-sufficiency  

Similarly, an intellectual disability involves the significant loss of cognitive functioning (e.g. ability to reason, problem-solve, think abstractly, learn from experience, and make complex plans) as evidenced by:

  • Appearance before the age of 18
  • Intelligence quotient (IQ) test score of less than 70; and
  • Significant deficits in adaptive behaviors in two or more ways

Intellectual impairment can be the result of a number of contributing factors including genetic conditions, medical complications during pregnancy or birth, traumatic brain injuries, or even a severe lack of environmental and social stimulation in early development.

The terminology we use (i.e. categories and labels) has profound consequences and it matters a great deal to the people who are referenced by our language (see the Respectful Language tab). While the term “mental retardation” may still be heard in a number of public and private spaces – and has been for over five decades – it has steadily been replaced in recent years by “intellectual disabilities.”