Trajectories of Intellectual Development in Autism

Tracking IQ over a 3-4 year period, in 4 sub-groups of 2-8 year olds

Today’s post is about trajectories of intellectual development in autism, which I have to come to believe is the most important aspect of autism and certainly helps you understand where your type of autism fits in.

As regular readers may recall average IQ = 100 and the IQ scale fits a bell-curve, so most (68%) people have an IQ within the range 85-115.  2.1% of the general population have an IQ less than 70, which is the cut off for a diagnosis of MR/ID (Intellectual Disability).

There are special tests to measure IQ in non-verbal people and IQ testing is matched to your age; so the older a child gets the more there is expected from them in the test.

I do wonder how you can fairly test the IQ of a 2 year old with severe autism. So I think some testing in very young children may substantially underestimate IQ. 

A study was recently published taking data from the Autism Phenome Project run by UC Davies.

What will my child's future hold? phenotypes of intellectual development in 2-8-year-olds with autism spectrum disorder.

Even though the sample size is only a hundred, what makes it interesting is that it is a longitudinal study, meaning they collect data from the same kids over a period of many years.

Welcome to the Autism Phenome Project

They fitted data from the hundred kids into four groups and then took the average IQs within each group. The kids had IQ measured twice, not at exactly the same ages, but about 4 years apart. (The youngest at T1 was two years old and the oldest at T2 was eight)

I used their data and apply my interpretation. I do not think they made the most of their own data.

So the first group (black) are the Asperger’s kids who were 22% of the sample group.  This group started out at 2-3 years old with IQ just under 100 but in the next 4 years they raised their cognition at an above average rate, so that average IQ rose to 110. Not bad going.   Average IQ in the general population is 100.

Classic autism is the red group at the bottom and as expected their IQ starts out low and gets worse, because they add skills at a lower rate then NT kids, so even though they learn, their measured IQ falls. This group was 26%.  Even though the sample is very small at 100, this is close to my estimate of classic autism (SDA) being about 30% of all autism. In some countries you have to measure IQ to access services. Our behavioral consultant was not a fan, because the parents get upset when IQ goes down over time, so we never measured IQ. The red line is even lower than I had expected.

The green line I called responsive autism, because even though IQ is low it does not fall during the 4 years period where it was measured. This group account for 18% of the total. These children are acquiring new skills at a fair rate.

The good news is the blue line; in that large sub-group of 35%, the kids had some kind of “dysmaturation” at time 1, allowing them to make rapid cognitive improvement in the 4 years after their diagnosis (Time 1). They have gone from a technical definition of MR/ID to getting close to average IQ.

It would be great to see what happens at Time 3. I suppose if we wait 4 years we may find out.

I think some of the 35% (blue line) likely did not perform to their full ability at the first test (at time 1), for which there are numerous reasons, not liking/being familiar with the tester being an obvious one.  Based on other sources from this blog, I think it is about 15% of autism cases that make such a dramatic improvement to the age of eight.

In the above study the type of intervention chosen by parents (how many hours of ABA, speech therapy etc) had no correlation with IQ improvement from Time 1 to Time 2. It is your biology that matters most and to tweak that you need a little help from chemistry, as some regular readers have discovered. 

Counter Argument 

There is a alternative view that IQ is not important in ensuring favorable outcomes in autism; this does sound rather odd. It is a view put forward not just by the small, but vocal, group with Asperger's promoting their "neurodiversity" ideas, but also some well paid researchers. In my chart above I used Asperger's for the black line representing the people with average IQ. In the actual paper they do not call it Asperger's.

Intelligence scores do not predict success for autistic adults 

This is a very recent, rather light weight, article and would be much better if titled "Intelligence scores do not predict success for Aspies."   

Aspies do indeed share some biological problems with people with severe autism, but their daily life problems are much closer to those faced by people with Schizophrenia or Bipolar. A good example is suicide, where it is extremely common in bipolar, said to be 10% (as cause of death) in schizophrenia and ten times the "normal" level in Asperger's.  In severe autism the suicide rate is zero, they may have accidents but do not try to kill themselves.

In someone with Asperger's and an IQ of 120, boosting their IQ to 140 will likely not help them; it would just make them feel more different. In a ten year old with severe autism and an IQ of 50, a child who cannot figure out which way round to put on his T shirt, cannot tie his shoelaces and does not understand why you need to cut your finger nails, a boost in IQ to 80 would be transformative. 

The education of people with severe autism focuses on adaptive behavior, or life skills. These are key skills for semi-independent living. These are skills that children of average IQ just pick up from observing the people around them. People with impaired cognitive function cannot just pick up these skills, they need to be taught (again and again and again).  I spent three years trying to teach prepositions to my son Monty to the age of eight, using a special computer program created for other people with exactly the same difficulty. Once I started addressing cognitive function, with Bumetanide, from the age of 9, Monty figured out prepositions all by himself, without any teaching. I never even bothered to use the remaining language teaching software that I had paid $1,500 for, as a bundle, when he was four years old.  It is still sitting unopened on the shelf.