The document provides a historical overview of the classification of intellectual disabilities in the U.S., highlighting the evolution of diagnostic criteria through various editions of the DSM from 1952 to 2013. It discusses the transition from the term 'mental retardation' to 'intellectual disability' in DSM-5, emphasizing the importance of limitations in intellectual functioning and adaptive behavior. Additionally, the document addresses measurement issues and the need for clinicians to use a comprehensive approach to diagnosis, considering factors beyond IQ scores.

1. Diagnosis/Assessment of
Intellectual Disability

3. Diagnostic System
In the U.S, the initial impetus for developing a classification of mental disorders was
the need to collect statistical information.
In 1840 information was collected based on Insanity/Idocy
By 1880 census, 7 categories of mental illness were distinguished
•Mania
•Monomania
•Paresis
•Dementia
•Dipsomania
•Epilepsy
The categories till 1917 primarily were statistical classifications.

4. The first edition (DSM‐I) was published in 1952, and had about 106
different disorders.
In DSM‐II, published in 1968 it grew to 140 disorders
In 1986 the DSM III‐ R appeared as a revision of DSM‐III. Many criteria
In 1994, it evolved into DSM‐IV and it contained 297 diagnosis
In 2000 DSM‐IV TR was published
In May 2013 DSM‐5 was published with 300 diagnosis
In 1980, with DSM‐III the number of diagnosis grew to 265
were changed and the diagnostic criteria’s grew to 295

5. Diagnosis of Intellectual Disability
• The term or name for condition we know today as intellectual
disability has changed over time; most recently the condition was
primarily known as mental retardation (DSM‐IV)
• Although the name has changed, for more than 50 years the three
essential elements for all definitions for this condition—limitations in
intellectual functioning, behavioural limitations in adapting to
environmental demands, and early age on onset—have not
substantially changed.

6. DSM‐5 Diagnostic Criteria
• Deficits in Intellectual functions, such as reasoning, problem solving,
planning, abstract thinking, judgement, academic learning, and
learning from experience, confirmed by both clinical assessment and
individualised standardized intelligence testing.
• Deficits in adaptive functioning in one or more activities of daily life
such as communication, social participation, and independent living,
across multiple environments, such as home, school, work, and
community
• Onset of intellectual and adaptive deficits during the developmental
period

7. Changes from DSM‐IV to DSM‐5
DSM‐IV DSM‐5
Terminology – Mental Retardation Terminology – Intellectual Disability
IQ 70 or Below Deficits in General Mental Abilities (70±5)
Concurrent Deficits or impairments in present
adaptive functioning in two or more domains
Concurrent Deficits in one or more domain across
settings (e.g., home and school)
The onset is before age 18 All symptoms mush have an onset during the
development period
Severity‐ mild, moderate, severe, profound based on
IQ level
Severity‐ mild, moderate, severe based on adaptive
behaviour

8. DSM‐5
• Reflects the growing concern about excessive & inappropriate
reliance on IQ cut‐offs for diagnosis
• Encourages clinicians to take into account various sources of test &
measurement error
• Encourages clinicians to consider & integrate information from a
broader array of sources

9. Measurement Issues
• ID is one of the diagnosis that has a reliance on
measurement – IQ and Adaptive Behaviour
• Reliable Measurement can be an issue when assessing
children under the age of 5, people who have comorbid
conditions such as autism or developmental trauma, or the
severity of the intellectual disability is such that assessing IQ
is not a feasible option
• There are issues when full‐scale IQ score may be invalid
when there is excessive scatter among subscales

10. • IQ scores are approximations of conceptual functioning and may be
insufficient to assess reasoning in real life situations
• The diagnostic criteria refers to intellectual functions that involve
reasoning, problem solving, planning, abstract thinking, judgment,
learning from instruction & experience, & practical understanding –
few of these abilities are tapped by IQ tests

11. Given the diagnostic and assessment issues
• A clinician does need to have expertise in both diagnosis and
assessment techniques
• It is never the diagnostic criteria that makes the diagnosis, it is the
responsible clinician that utilises the criteria to make the diagnosis