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ICD-10 Diagnostic Criteria

ID represents a group of conditions characterized by impairment of skills manifested during the neurodevelopmental period, skills which contribute to the overall level of intelligence, i.e. cognitive, language, motor, and social abilities*. ID can occur with or without any other mental or physical condition.

Intellectual abilities and social adaptation may change over time, and, however poor, may improve as a result of training and rehabilitation. Diagnosis should be based on the current levels of functioning. Degrees of ID are conventionally estimated by standardized intelligence tests. These can be supplemented by scales assessing social adaptation in a given environment. These measures provide an approximate indication of the degree of ID. The diagnosis will also depend on the overall assessment of intellectual functioning by a skilled diagnostician.

If desired, additional codes are used to identify associated conditions such as autism, other developmental disorders, epilepsy, conduct disorders, or severe physical handicap.

A fourth-character subdivision is used to further signify ID categories (F70-F79) in order to identify the extent of impairment (or severity):

  • .0 With the statement of no, or minimal, impairment of behavior

  • .1 Significant impairment of behavior requiring attention or treatment

  • .8 Other impairments of behavior

  • .9 Without mention of impairment of behavior

F70 Mild

Approximate IQ range of 50 to 69 (in adults, mental age from 9 to under 12 years). Likely to result in some learning difficulties in school. As adults individuals will be able to work and maintain good social relationships and contribute to society.

F71 Moderate

Approximate IQ range of 35 to 49 (in adults, mental age from 6 to under 9 years). Likely to result in marked developmental delays in children but most can learn to develop some degree of independence in self-care and acquire adequate communication and academic skills. As adults they will need varying degrees of support to live and work in the community.

F72 Severe

Approximate IQ range of 20 to 34 (in adults, mental age from 3 to under 6 years). Likely to result in continuous need of support.

F73 Profound Mental Retardation

IQ under 20 (in adults, mental age below 3 years). Results in severe limitation in self-care, continence, communication and mobility.

F78 Other

F79 Unspecified

Individuals who have an age of onset after 18 qualify for the diagnosis qualify for F78 Other, and in those IQ range is not known, it is referred to as F79 Unspecified.

Adapted with permission for International Statistical Classification of Diseases and Related Health Problems 10th Revision <>

*Intellectual Disability (ID) has gained universal usage replacing the term Mental Retardation (MR). In this chapter and table we refer to ID as synonymous to MR under the World Health Organization (WHO) International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10). This is expected to change under the 11th revision (ICD-11) forthcoming in 2018.


Intellectual Disability ...

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