Duhaime's Law Dictionary

Mentally Retarded Definition:

Subnormal general intellectual functioning which originates during the developmental period and is associated with impairment of learning and social adjustment or maturation.

Related Terms: Mentally Ill, Incompetency, Non Compos Mentis

Significantly subaverage intellectual functioning.

Mental retardation is a mental disorder which is usually congenital, usually observed and diagnosed from birth or in childhood.

The American Psychiatric Association, in their DSM-IV Manual defines mental retardation as follows:

"Significantly subaverage intellectual functiong - an IQ of approximately 70 or below - with onset before the age of 18 years and concurrent deficits or impairments in adaptive functioning."

According to the DSM-IV catalogue of mental disorders, mental retardation can be:

  • Mild;
  • Moderate;
  • Severe; or
  • Profound.

But other publications1 suggest five classes of severity: borderline (an IQ of 68-83), mild, moderate, severe and profound, whereas some general medicine publications suggest eight scales of severity.

Mental retardation is distuiguished, as a mental disorder, from learning, attention deficit or anxiety disorders.


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