Autism or Intellectual Disability: How Can We Know?

IH Asks

We have a child with Autism Level 1, possibly Level 2. They are soon to undergo an assessment for Intellectual Disability (ID), and the child is nearly 7 years old. Our child is significantly behind their peers academically and socially. However, they’ve recently started to show an interest in letters.

How can an ID assessment in this age range truly reveal what’s going on? They are intensely interest-driven, and as parents, we don’t understand how this will be possible. They are very different socially, and we often wonder if it’s simply autism. We also feel that, in terms of age-appropriate development, they seem considerably younger in how they speak and behave compared to their peers.

Paula Responds

Thank you for your questions! I’ve decided to break them up and publish your second question next week, but no later than then. Today, I’ll answer your question about Intellectual Disability (ID), and I’ll address your other question about social training at a later date. I hope you don’t mind me splitting it up like this! I simply have so much to say about social training that I was afraid the response would be too lengthy if I answered both questions in one post.

It Can Be Difficult to Distinguish Between Diagnoses

You’re right to feel it can be difficult to differentiate between autism and ID, and I understand your uncertainty. While the diagnostic criteria for autism and ID differ—those with ID have difficulties in both intellectual and adaptive functioning, while autism is characterized by social challenges and restricted interests or behaviors—it can sometimes be hard to separate the two in practice and determine the root cause.

ID Can Present Social Challenges

Autism researcher Christopher Gillberg writes in his book that children with ID can be socially immature and struggle to interpret social cues. He also argues that children with ID can be cognitively inflexible, have poorer motor skills, struggle with prioritization, use concrete language, be socially naive, and have a different way of communicating. Special education teacher Helen Carlander also presents case studies of children with ID who have difficulty remembering information that doesn’t interest them. When you read literature on autism, you’ll find many of the same characteristics are often described in individuals with autism!

Good That Your Child Is Being Assessed

I believe that an experienced and competent clinician should be able to distinguish between autism and ID and assess whether a child’s challenges stem from a lack of interest or impaired intellectual ability. This is something only someone with the right expertise can determine! Gillberg notes in his book that diagnosing ID isn’t always easy, and many with mild ID remain undiagnosed or receive a diagnosis only as adults. Gillberg also writes that ID requires educational adaptations, and a child whose diagnosis remains undetected risks developing social and emotional problems. Therefore, it’s positive that your child is being assessed now!

ID Is an Unpopular Diagnosis

Finally, I want to share a few thoughts. I’ve noticed in my work as a lecturer that many parents react strongly when their child is diagnosed with ID. It’s not uncommon for them to hope their child has autism instead. And if a child has learning difficulties in school and their IQ is 75, they might think it’s better that they simply have a lower-than-average IQ rather than ID. Christopher Gillberg writes that the ID diagnosis has become unpopular, which I think is unfortunate. I want to try to normalize it, as you are still the same person regardless of what diagnosis you have.

The Diagnosis Can Be Helpful

It’s important to remember that an ID diagnosis can actually be helpful if a child struggles to keep up in school. For example, children with ID are entitled to attend adapted basic education (formerly known as special school), which isn’t currently the case for children with lower-than-average IQs who don’t have ID. Even though an ID diagnosis can feel significant, it doesn’t have to be. In some cases, it can make it easier to get the right support!

You Can Live a Good Life

Furthermore, Lena Nylander writes in her book that autistic individuals with ID more often report a higher quality of life than autistic individuals with high intelligence. So, you shouldn’t fear ID. Certainly, autism with ID often means greater support needs than individuals with “just” autism, but with appropriate support, you can live a good life with both autism and ID!

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Don’t be afraid to reach out for help if life feels hopeless! Here’s a list of helplines and phone support services in the US you can contact if you need assistance. For people outside the US this page lists helplines for people in need of immediate mental help support during a mental health crisis.