Abstract
Judith L. Rapoport, F. Xavier Castellanos, Nitin Gogate, Kristin Janson, Child Psychiatry Branch; Shawn Kohler, Phillip Nelson, Section on Neurobiology, Laboratory of Developmental Neurobiology Branch; National Institute of Mental Health, Bethesda, Maryland, USA:
Dr Halasz's suggestion that ‘research studies on ADHD are based on the assumption that the condition has been “proven” to exist’ appears to place the cart before the horse. First, scientific theories are never truly proven, only supported by increasingly converging evidence, or alternatively, disconfirmed, and replaced by a better fitting theory. The corollary is that research studies are based on the assumption of the null hypothesis, which in this case could be captured by the statement that ADHD is not ‘a brain disorder’. It is in this context that the accumulating weight of non-invasive brain imaging studies discussed in our review should be considered. In particular, magnetic resonance imaging now permits the ‘collection’ of sufficiently large samples of the organ of interest along with prospective re-scans of the brain across development. These and other techniques are increasingly assisting the delineation of the neurobiology – or lack of same – for a variety of disorders currently still defined behaviourally. We believe that it is only through a genuine understanding of the pathophysiology of conditions such as ADHD that the conundrum described by Dr Halasz will be solved.
We also need to point out that the cited commentary by Dr Jensen [1] is not the same as the Consensus Development Conference Statement [2], although the two were published adjacently. The latter makes no reference to ‘proven’ or ‘unproven’ status although it does conclude that ‘further research is necessary to firmly establish ADHD as a brain disorder’, a position with which we strongly concur.
Finally, we agree with Drs Halasz and Jensen that ADHD should not be ‘reified’. However, until a better system comes along, ADHD remains a reliable and reasonably valid DSM-IV diagnosis. With the increasingly rapid emerging of new research tools, we expect that there will be far reaching changes across the entire diagnostic spectrum.