(Note:  This post summarizes content found in my new book Child Temperament: New Thinking About the Boundary Between Traits and Disorders.  If you like what you read, I urge you to find out more)

Blood pressure is not a disease.  All of us have one and the numbers, if measured across a large sample of people, fall into one of those classic bell-shaped curves. At a pressure above 140/90, however, that characteristic becomes an illness and worthy of treatment with remedies ranging from a low-salt diet to prescription medications.

Modern psychiatry, however, has resisted such a conceptualization of its conditions, opting instead for more of an all-or-none model in which a person either does or does not have a psychiatric illness.  Our temperament or personality traits, it follows, don’t have much to do with these disorders.  Happy people can get depressed, and fearless people can develop anxiety disorders.

Certainly there are many cases where such presentations are true, but are the worlds of personality and psychopathology really that distinct?  Accumulating research studies are consistently saying that they are not, and that many if not most disorders exist not in a binary yes-no form but as more of a spectrum or continuum, not unlike blood pressure.  The relation between a child’s activity level or attentional abilities and the diagnosis ADHD is likely one of the best examples of this phenomenon.  Moreover, there is good reason to suspect that the “speed limit” between what is considered a normal and abnormal level of behavior has been dropping over the past several decades from everything from ADHD to autism to bipolar disorder.  This shift is likely responsible for at least some of the “epidemic” rates of psychiatric disorders observed today, despite other evidence that the overall level of problem behavior in children has remained fairly constant. 

Whether that is a good or a bad thing is reserved for another posting (or your comments) but there certainly may be both positive and negative elements.  A crucial missing piece to this challenge, in my view, is neuroscience.  While there may be little on the surface to distinguish between the “quite active” from “hyperactive” child, what we really need to know (and don’t) is whether or not there is something qualitatively different in the brains of kids with ADHD or whether whatever factors conspire to determine a child’s activity level are merely amplified in those with ADHD.  Hiding within other bell-shaped curve distributions like intelligence are folks whose challenges are due to something more distinct, like having an extra 21st chromosome that causes Down Syndrome.  Whether similar processes will be found for psychotic symptoms, or mood, remain to be seen.

In the meantime, there may be some real benefit from fully accepting a more dimensional view of psychiatric disorders that embraces its relations with temperament and personality.  For one, such a perspective might be less stigmatizing.  Rather than a child being told that he “has” ADHD, it can feel much more inclusive to be told that everyone lives on this spectrum somewhere and that he is somewhere near the top but can bring that level down with some intervention and hard work.

Ironically, our effort to legitimize psychiatric disorders by treating them like a true medical illness may have backfired on us by implying much more of an “us versus them” view than the science bear out. 

copyright by David Rettew 2013

David Rettew is author of Child Temperament: New Thinking About the Boundary Between Traits and Illness and a child psychiatrist in the psychiatry and pediatrics departments at the University of Vermont College of Medicine.

Follow him at @PediPsych and like PediPsych on Facebook.

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