Intelligence is not a good estimate of functional levels in children diagnosed with autism

It is hard to come across any terms more widely used in our field than ‘high functioning autism’. While the term was coined by researchers in the 1980s, it is a commonplace label heard in clinics, schools, and even in mainstream media depictions of autism.

The term was originally devised by researchers to distinguish between individuals with and without co-occurring intellectual difficulties (the average IQ is 100, and scores less than 70 suggest a person may have an intellectual difficulty). However, ‘high functioning autism’ is not an official diagnostic term in diagnostic manuals. The term was also sometimes used interchangeably with Asperger’s syndrome until the introduction of Autism Spectrum Disorder in 2013.

New research published by our research team provides evidence to indicate why this term should no longer be used.

Why is using ‘high functioning’ an issue?

Many autistic people have long advocated for this term to be abandoned due to its inaccuracy; using this sort of functioning terminology comes with assumptions of someone’s abilities that may not match what the individual is capable of.

‘High functioning’ presumes functional strengths that an individual may not have; by contrast, ‘low-functioning’ comes with preconceptions of not having strengths or abilities.

In other words, just because a person has typical or expected intellectual abilities, does not necessarily mean they have good functional skills for their age.

What does ‘functioning’ mean?

When we refer to functional level, we’re often referring to an individual’s adaptive skills; those practical skills or behaviours necessary to function in everyday life. This can include being able to communicate (verbally or non-verbally), interact with peers and cope in social situations, and learn domestic and independent living skills (e.g. take public transport, prepare food, or understand self-care).

Research indicates that individuals with an autism diagnosis are more likely to have greater adaptive functioning difficulties relative to their peers of the same age. Other research also indicates that rates of skill acquisition may also be slower, so that as autistic individuals get older, adaptive skills may become increasingly more challenging, relative to what we would expect for their age.

What does this new study show?

In this study, we reviewed data from 2,225 children and young people (aged 1-18) diagnosed with autism, about half of whom had intellectual disability (IQs < 70), and half of whom did not.

This data came from a very large and ongoing registry of data from individuals diagnosed with autism in Western Australia, collected since 1999. This data was collected at the time a clinician made a diagnosis, so this data represents what an individual’s functional level was like at the time they are seen for a clinical evaluation of autism.

We analysed their estimated cognitive level (IQ) and functional abilities, measured using the Vineland Adaptive Behavior Scales.

We found those with an intellectual disability had functional skills which closely matched their reported IQ. However, those typically deemed to be ‘high functioning’, due to having an average or higher IQ, had functional abilities well below what would be expected, given their IQ.

What do these findings indicate?

These findings suggest that those without an intellectual difficulty, who would have been called ‘high functioning’, have marked challenges with their everyday skills relative to what we would typically expect given their IQ.

In other words, IQ was a poor predictor of someone’s functional level, particularly for those individuals who do not have an intellectual impairment.

The implication of this study is that children given this ‘high functioning autism’ label are not just presumed to have better functioning than they really do but exhibit far greater challenges with everyday skills than the label would suggest.

Using the label ‘high functioning’ is not just inaccurate, but potentially results in disadvantage. The term underplays the challenges autistic individuals often experience on a day-to-day basis and leads to misleading expectations about their abilities to function in the environment, whether that’s at school, work or elsewhere.

It’s also often used as a means of understanding whether an individual may need to access funding and services. It might be used, for example, to argue that a child should be able to go to a mainstream school without support when they may still struggle with skills like understanding instructions, note-taking, self-care, changes to routine, or interacting with their peers.

By continuing to use this label, we may be inadvertently perpetuating a cycle that denies people access to services and support that they need, based solely on their IQ.

This research also suggests that comprehensive functional assessments should be done at the time of a diagnostic evaluation to help understand an individual’s challenges, as well as their strengths.

Dr Gail Alvares
@gailalvares
Telethon Kids Institute