Impulsive - what does that really mean?

This is the second of three reports from the 2011 annual meeting of the Maryland Association for Behavior Analysis (MABA). 


As higher functioning children with ASD progress and succeed, their diagnosis may be questioned.   In my son’s case, he was diagnosed in Infants and Toddlers days as having Asperger’s Syndrome.   By elementary school, he had responded so well to early intervention that school staff couldn’t see it and believed he had ADHD all along.  ASD, as you may know, is the only disorder where if you improve you never had it in the first place.  

Once we had more thorough-going assessments done in the process of transferring him to a private special needs school, we learned they were both partly right.    He would be most succinctly described by an Asperger’s diagnosis, based on how he presents today.   But he doesn’t meet criteria because he had speech delays before age 3.  So back then, he should have been diagnosed with autism.   He has progressed so far, he now doesn’t meet criteria for autism.  He does meet criteria for ADHD, but it doesn’t begin to explain all his needs.   It takes several pages of specific learning disabilities to paint the rest of the picture.

Since we have experienced how blurry the boundary between Asperger’s/high-functioning autism and ADHD can be, I was very interested when Dr. Leonard Green presented at MABA this year about one factor which may be blurring the line.   Green, a professor of behavioral psychology at Washington University in St. Louis, discussed one of the diagnostic criteria of ADHD – impulsivity. 


 

When we describe a person as impulsive, Green said, we may mean a variety of things.    We may say a person is impulsive if they can’t wait for rewards or act without forethought, traits related to how they deal with delay.   We may also say a person is impulsive if they are prone to risk-taking or can’t resist temptation, traits related to how they deal with the probability of risk.   

Green presented data from experiments in behavioral discounting – tests of whether individuals would prefer something now vs. more later or something guaranteed vs. the possibility of something more.    At first glance, the data appear to show the same thing, a consistent curve that tracks how the value of a reward decreases as the delay or odds against it increase.   But the picture changes if you put both results together for the same individual – impatience and risk-taking aren’t correlated, the distribution of both traits across individuals is random.    So what we call ‘impulsiveness’ is really two different things.

Why does this matter for diagnosis?  Impulsivity is a named criterion for ADHD in the DSM-IV.   The authors of the diagnostic manual are not confusing two things – the examples they give all relate to impatience (e.g. ‘blurts out answers,’ ‘has difficulty waiting for turn’).   But clinicians in schools and treatment centers rarely have the book open when taking about diagnosis with parents.  They may use ‘impulsivity’ more loosely when making a case that a high-functioning ASD kid has ADHD instead.  

In my son’s case, this didn’t happen – his impulsivity is all delay related; he’s not a risk-taker.  But it’s easy to imagine a child taking risks due to failure to select the pertinent stimuli in their environment that signal risk or failure to understand a social context that creates risk.   These traits are related to ASD.   If such a child’s risk-taking impulsivity were used to view them as ADHD, it could lead to misunderstanding, misdiagnosis and missed treatment opportunities.   Understanding this word matters.

Wil Gehne