What is an intellectual disability?

Dr Mark Lovell is a Consultant Child and Adolescent Intellectual Disability Psychiatrist, Tees, Esk and Wear Valleys NHS Foundation Trust. He is an ACAMH Board Member and the Lead for CPD and Training.

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An Intellectual Disability (ID) also known as a Learning Disability, is reflective of an IQ below 70 with adaptive behavioural difficulties (daily living skills). This would place an individual’s IQ in approximately the bottom 2% of the population i.e. outside of the ‘normal’ range. There are various classification systems in place. An ID can be classified as mild (IQ 50-69), moderate (IQ 35-49), severe (IQ 20-34) or profound (IQ less than 20).

The Identification of an Intellectual Disability, an A to H Framework (IDID A2H©): short version

The following alphabetical framework is designed as an aide memoire for the identification of an ID (in children, young people or adults). It will help you identify available information sources and gaps in knowledge about an individual’s ability. It will guide you in decision making regarding a likely diagnosis and help you generate a needs based plan.  It can be used by any professional working with children and young people.


Gather current, predicted or historical attainment from education. Compare this against established expectations for an age group. Information may be from school or college reports, a teacher or the results of tests or examinations. If out of education, it is important to consider how much education was received, whether it was in an appropriate setting and what attainments were made.

Consider the context of an individual’s education e.g. attendance, engagement or any factors such as behavioural problems that interfered with attainment.

Diagnoses may have already been made e.g. specific or generalised learning difficulties. Understanding what these are and their severity is important.

Behaviours of daily living

These are also known as adaptive behaviours of activities of daily living. They reflect a range of skills that develop over time.

An ID requires evidence of significant delays in adaptive behaviours. Tests can contribute towards understanding the degree of delay in adaptive behaviours.

Cognitive assessments

Formal assessments of cognition are important in the making of an accurate diagnosis of an ID. They produce a full scale IQ score with sub- sections that cover areas of skill or difficulty. These are required to classify an individual as having an ID.

A variety of IQ tests are available covering different ages or levels of verbal ability.

There are limitations to cognitive assessments. IQ is supposed to be stable over time, however it can worsen if; an individual is losing skills or ability or if they are choosing or unable to engage with the testing or if their primary language is not English or they are not able to engage, communicate or focus.

Short screening IQ tests are available. They may be useful for establishing a likelihood of an ID

Development (other)

Development occurs in a range of areas and at different rates. Physical development includes growth, fine motor, gross motor and sensory. Socio- emotional development includes social skills, the development of attachments, play and behaviours. Other areas of development include sleep, speech, language and communication. Consider specific or more generalised delays. The degree of developmental difficulty should also be considered.

The presence of differing patterns of developmental delays may indicate other conditions e.g. a speech, language or communication disorder or other neurodevelopmental disorder.

Environmental Influence

Consider an individual’s environment(s) and whether they are supportive of development and learning.

Factors (other)

Other conditions maybe masked by the ID, or mask the ID itself. This is called diagnostic overshadowing. Other neurodevelopmental conditions are likely candidates for diagnostic overshadowing.

Mental Health and Behavioural disorders as well as physical health problems are more common and presentations may be atypical. E.g. tooth ache may present as challenging behaviour.

Attachment difficulties may also present following early childhood adversity and differences in parental responses to a child with a disability. Rates of abuse and need for safeguarding may also be higher than the general population.

Underlying reasons for an ID may be present e.g. genetic makeup.

General Impression

  • Not an ID i.e. IQ and/or adaptive functioning are within normal range, alternative diagnoses or formulations should be considered
  • Possible ID i.e. further investigation is required over time
  • Confirmed ID i.e. IQ is 70 or below and there are significant difficulties with adaptive functioning

How to meet an individual’s needs?

Generate a person centred multiagency, multidisciplinary plan to meet the needs identified in A to G. communicate the findings and plan to the individual’s network.

Key Points

  1. A structured approach to identifying an ID can assist in making a diagnosis and promote each person being considered as a unique individual.
  2. Identification requires more than just an IQ score
  3. Alternative diagnoses/formulations should be considered
  4. Meeting needs is more important than just identifying an ID

You can watch ‘(IDID A2H©) Identification of Intellectual Disabilities Framework (Children, Young People and Adults) – Dr. Mark Lovell’ on our YouTube channel.

The IDID A2H© framework is free to use clinically. It can be reproduced for non-commercial uses. Any publication in hard copy or electronically requires permission from the author, acknowledgement of the copyright and authorship. No reasonable request will be refused. Contact Mark.Lovell@NHS.net.


This looks interesting Mark – How do I obtain a copy of the IDID A2H Framework?

Best wishes

Dr John Mallen, Clinical Neuropsychologist

Of the neurodevelopmental conditions, autism frequently misleads the observer, leading them to exclude or to assume ID for the level of ability can vary widely in different domains.
Speech, whether fluent or very limited, often leads someone to assume automatically that there is a similar level of comprehension and too often the phrase ‘oh, he can understand everything’ delays a careful assessment.

Levels of cooperation with testing may be so variable, making it occasionally impossible to reach a valid conclusion, particularly with autistic people but also with very anxious, angry or physically unwell people. Sensible carers or relatives who have known the person for some time may provide the best information.

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