What is Intellectual Disability?

In the last year, I have seen more questions about intellectual disability from members on and off the page.  I have taken some information from IHC and the DSM 5, plus some research and webinars and put this document together today to help members. It’s not perfect but it’s a place to start your journey.

Intellectual disability is a term used when a person has difficulty understanding, concentrating, learning and remembering new things in their everyday life.

People with an intellectual disability may need support to develop new skills, understand complex information and communicate with other people. An intellectual disability almost always becomes evident during the developmental years. Despite certain limitations, people with an intellectual disability often have other strengths and capabilities.

People with intellectual disabilities are all very different individuals. Some have additional health problems or disabilities that can make their lives harder. Disability is not an illness, but does require people to have some support for daily living.

The IHC use the term intellectual disability as it is the most commonly used phrase and it is endorsed by leaders and activists with an intellectual disability. You may come across the terms learning disability, developmental delay or special needs on other websites and resources.

What is IQ?

IQ, short for intelligence quotient, is a measure of a person’s reasoning ability. In short, it is supposed to gauge how well someone can use information and logic to answer questions or make predictions

Different types of intellectual disabilities

There are different types of intellectual disabilities, which can be classified as mild, moderate, severe or profound. In all cases an intellectual disability is lifelong. These categories are not rigid and there are no clear dividing lines between the different groups. It’s important to realise that language is constantly changing. The words we use to describe intellectual disability have changed over time, and will continue to change, as a result of listening to people with personal experience and as a result of changing values and attitudes in society.

IHC believes it’s more useful to address how much support a person with an intellectual disability might need instead of classifying to which group they belong. However, an agreed definition can be useful to let us know which people will be included for funding and support, how to diagnose it and how to plan supports for people to live satisfying lives in the community.

Disorder Characteristics as per the DSM 5

Intellectual disability involves impairments of general mental abilities that impact adaptive functioning in three domains, or areas. These domains determine how well an individual copes with everyday tasks:

• The conceptual domain includes skills in language, reading, writing, math, reasoning, knowledge, and memory.
The social domain refers to empathy, social judgment, interpersonal communication skills, the ability to make and retain friendships, and similar capacities.
The practical domain centres on self-management in areas such as personal care, job, responsibilities, money management, recreation, and organizing school and work tasks.


In New Zealand, Educational Psychologists and Psychologists are the only ones who can diagnose an Intellectual disability. 

The links below will answer some questions about the assessment WHO CAN DIAGNOSE IN NEW ZEALAND?


Comprehensive Assessment –

DSM-5 emphasizes the need to use both clinical assessment and standardized testing of intelligence when diagnosing intellectual disability, with the severity of impairment based on adaptive functioning rather than IQ test scores alone. By removing IQ test scores from the diagnostic criteria, but still including them in the text description of intellectual disability, DSM-5 ensures that they are not overemphasized as the defining factor of a person’s overall ability, without adequately considering functioning levels. This is especially important in forensic cases.-

It is important to note that IQ or similar standardized test scores should still be included in an individual’s assessment. In DSM-5, intellectual disability is considered to be approximately two standard deviations or more below the population, which equals an IQ score of about 70 or below. The assessment of intelligence across three domains (conceptual, social, and practical) will ensure that clinicians base their diagnosis on the impact of the deficit in general mental abilities on functioning needed for everyday life. This is especially important in the development of a treatment plan.

Mild Intellectual Disability

For the purpose of this document and for the deb page I will talk about Mild Intellectual disability. I have attached links at the end of this document for those who would like to learn more about Moderate, Severe and Profound.

Quick reference Questions

Can my child learn?

Yes, your child can learn it will be harder and it will take longer for them to master and generalise/transfer the information in day-to-day situations.

What approaches should I use to teach my child?

The best approaches are evidence-based approaches. Treat reading as if it was dyslexia, and math as if it was dyscalculia. Language issues as if it was a Language developmental disorder (DLD) and writing as if it was dysgraphia or it might come under dyspraxia.

Head to www.deb.co.nz for information on dyslexia, dyscalculia, DLD and dysgraphia

For Social skills we recommend you look at evidence-based approaches used with autistic children. The interventions are the same for a child who has a mild intellectual disability.

Will teachers and schools understand what my children’s needs are?

The odds are no teachers are not trained in any of the conditions I have listed in this document. Unless the teacher or the school has personally paid for training themselves. It will be up to work with the school to get the right support, interventions and approaches in place.

Extra Information

A child with mild intellectual disability will normally present with an uneven learning profile and can show mastery in certain skills in class one day but can’t use these skills when they are needed the next day.  They can normally learn well in isolation. This can be very confusing for teachers and parents. The biggest challenge for children with ID is adaptive skills, transferring the knowledge they know to all areas of learning which is why this s now considered the main part of the diagnosis.

The information I have provided was taken from these documents and webinars



Dr Jill Allor’s research on teaching children with Intellectual disability


Dr. Jill Allor presents an overview of the elements of direct, systematic reading instruction for students who struggle to read, including students with intellectual disabilities. https://www.youtube.com/watch?v=ePdeV6v5FHg

Understanding Intellectual Disability Definitions, Intervention, and Resources



 This Document was created by Sharon Scurr