A Brain Test for ADHD?

One the problems with psychiatric diagnosis is that we do not have "objective" measures that rule the diagnosis in or out in the same way that medical blood tests and the like do. I put "objective" in quotations because even blood tests are much more subjective than we might think.

A psychiatric diagnosis is made by identifying and categorizing behavioral symptoms.  For example, if a patient exhibits a certain number symptoms (five out of eight for example) listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM) for a given duration, they qualify for the diagnosis. Absent from this schema is any real understanding of the reason for the symptom, it's function as a coping strategy. At the turn of the century Freud wrote of the need to understand the "sense" or meaning of symptoms rather than their mere existence (Freud, 1920. Introductory Lectures on Psychoanalysis). 

A new "objective" test has been approved by the FDA for the diagnosis of ADHD:

From the New York Times http://www.nytimes.com/2013/07/16/health/brain-test-to-diagnose-adhd-is-approved.html?partner=rss&emc=rss&smid=tw-nytimes&_r=0

"The test uses an electroencephalogram, or EEG, with sensors attached to a child’s head and hooked by wires to a computer to measure brain waves. It traces different types of electrical impulses given off by nerve cells in the brain and records how many times those impulses are given off each second.The test takes 15 to 20 minutes, and measures two kinds of brain waves — theta and beta. Certain combinations of those waves tend to be more prevalent in children with A.D.H.D., the Food and Drug Administration said in a news release."

 So will this eliminate our uncertainty when making a diagnosis of ADHD?  Probably not.  Our diagnostic system or nosology rests on a false belief in the reality of diagnostic categories.  In reality there is no such thing as "depression"or "ADHD."  I do not mean to imply that people do not suffer or that their lives are not impacted by these disorders, only that as an objective reality, these diagnoses are just constructs, ways of organizing phenomena into categories.

Without getting too philosophical (professors can get that way), suffice it to say that EEG's and medical tests exaggerate the certainty with which we draw conclusions.  We still do not know that a patient has ADHD even if they test positively on this new procedure.  What is more important is understanding the context and function of the symptoms so that we can help the patient.  As Freud pointed out, we need to make sense of the symptom and not just categorize them.