The Devil is in the Details: Differentiating High and Low Functioning in Autism

I have recently begun to contemplate a research project addressing the nature of interventions for individuals with autism.  As I begin to formulate the steps involved, it struck me that I would need to actually define what is meant by low- and high-functioning.  At first glance, my thinking was that this concept should already be both well defined and cited as these are concepts that are in widespread use.  But the reality is that there are no accepted definitions for low- and high-functioning on the spectrum.(Szatmari, 2000)  While most researchers use this terminology, few actually take the time to define it’s meaning or do so in tremendously diverse ways.

I pause here to briefly address the concern that terms such as low- and high-functioning are pejorative.  I appreciate that some will not like the idea of putting what seem limiting labels onto the disabled.  I have no desire to undertake research where I have to categorize individuals in this manner.  The problem, however, is that I have to review vast amounts of research looking at intervention programs and determine what segment of the spectrum such programs are intended to address.  Understanding how researchers determine who is low- and who is high-functioning is obviously vital.

So back to the problem at hand:  determining what is actually meant by the terms low- and high-functionin

g.  It turns out, it means lots of different things.  God Bless blogdom because I actually found a contribution by one Michelle Dawson where she investigated this very premise.  Her very brief review of the literature indicates level of functioning is typically based on scores of IQ or other tests of developmental ability.  The threshold separating high and low functioning in the literature that she reviewed is somewhere in the 50-90 IQ range, which is a tremendous span.   So large in fact as to make application of the IQ somewhat useless in terms of differentiating low- and high-functioning.

The DSM-5 takes us in a different direction.  For those that don’t know it, the DSM-5 is The American Psychiatric Association's Diagnostic and Statistical Manual, Fifth Edition.  The DSM-5 is used universally for psychiatric diagnoses in the United States and provides information regarding etiology, prevalence, age at onset, and prognosis.   It is also that opus that brought us the broadly inclusive label of “Autism Spectrum Disorder” which incorporates a number of previously determined autism subtypes under one big umbrella.

The DSM-5 skirts the issue of low- and high-functioning with “Severity Levels”.  Level 3 indicates an individual that requires very substantial support; level 2 is for those just needing substantial support.  Individuals with Level 1 autism are those requiring mere support.  This of course leaves open the question of individuals on the spectrum who do not require support, for example those who previously had an Asperger’s designation.   An even bigger problem with severity levels is determining what constitutes very substantial, substantial, and mere support and how this would be quantified. (Weitlauf, Gotham, Vehorn, & Warren, 2014)

A really lazy way of ascertaining low- and high-functioning is to simply equate low functioning with intellectually disability (ID).  This is not an effective means of categorizing as some individuals with ID have aptitude for the activities of daily living (hence functioning).  That is, low-functioning and intellectual disability are not synonyms, though low-functioning individuals are likely to have ID.

Yet another way to approach this issue is via a variety of ratings scales such as the Autism Diagnostic Observation Scale—Second Edition (ADOS-2) which is a means for determining the level of ASD symptoms (given age and language ability) utilizing a Comparison Score (CS). This tool appears to have some value as it allows for longitudinal change and is less reliant on verbal IQ (Gotham, Pickles, & Lord, 2009)  but is not in widespread use.  There are a variety of other comparable tools; take your pick.

There are a host of other problems as well, some big and some small, in differentiating between low- and high-functioning.  What is the relationship of functioning level with development?  That is, can individuals progress in functioning as they age?  And on what aspects of autism should level of function be based?  For example, if you focus exclusively on communication, then how do you categorize individuals who have severe echolalia?  Do you discount some speech and not others?  As always, the devil is in the details.

It is not lost on me that simply mapping all of the information related to determining low- and high-functioning on the spectrum would make a powerful research project in itself.  Such a project, however, would really be more appropriate from a psychological rather than a nutritional perspective.  Therefore, I leave this headache to someone else.

So, the categories of low- and high-functioning are indeterminate and hazy, which complicates the work ahead for me.  Creative ways around this problem are going to be needed, and likely already exist.  I will just have to find them.

References Cited

Gotham, K., Pickles, A., & Lord, C. (2009). Standardizing ADOS scores for a measure of severity in autism spectrum disorders. Journal of Autism and Developmental Disorders, 39(5), 693-705. doi:10.1007/s10803-008-0674-3

Szatmari, P. (2000). The classification of autism, Asperger's syndrome, and pervasive developmental disorder. Can J Psychiatry, 45(8), 731-738.

Weitlauf, A. S., Gotham, K. O., Vehorn, A. C., & Warren, Z. E. (2014). Brief report: DSM-5 "levels of support:" a comment on discrepant conceptualizations of severity in ASD. Journal of Autism and Developmental Disorders, 44(2), 471-476. doi:10.1007/s10803-013-1882-z