Researcher see flaws in brain-imaging studies
Insight on the News, August 19, 2003
by Kelly Patricia O'Meara
A recent review by Jonathan Leo, professor of anatomy at the Western University of Health Sciences in Pomona, Calif., and professor David Cohen of the School of Social Work at Florida International University in Miami, dispels the myth of brain imaging as a way to diagnose ADHD. And it finds that the majority of studies dating back to 1978 failed, unaccountably, to consider a major variable the use of psychotropic drugs by participants in the studies.
ED: What's interesting is that MRI, PET scans, and other imaging technologies are never used in the diagnosis of ADHD, only in research on potential causes or structural differences. So why the authors should be dispelling "the myths of brain imaging as a way to diagnose ADHD" is beyond us, since they are not used this way."
Leo and Cohen's review, entitled "Broken Brains or Flawed Studies? A Critical Review of ADHD Neuroimaging Research," was published last month in the Journal of Mind and Behavior and looked at 33 of the most recent studies using computerized topography, magnetic resonance imaging (MRI), single photon emission computerized topography or positron emission topography on ADHD-diagnosed subjects.
Although 14 scientists contributed to the study, it is generally referred to as the "Castellanos study" after the lead scientist, child psychiatrist F. Xavier Castellanos. Ten years in the making and unknown millions spent, Castellanos and his team conducted 544 MRI scans of 291 subjects 152 ADHD-diagnosed patients and 139 control subjects (normal). The Castellanos results were that "on initial scan, patients with ADHD had significantly smaller brain volumes in all regions, even after adjustment for significant covariates."
The celebrated doctor further concluded that "developmental trajectories for all structures, except caudate, remain roughly parallel for patients and controls during childhood and adolescence, suggesting that genetic and/or early environmental influences on brain development in ADHD are fixed, not progressive and unrelated to stimulant treatment." In other words, kids diagnosed with ADHD had smaller brains than those kids in the "normal" control group, and brain size isn't due to drug use.