The Supposed Physical Basis for ADHD

A study led by NIMH s Alan Zametkin et al. (1990) received a great deal of publicity for finding increased brain metabolism in PET scans of adults with a history of ADHD in childhood. However, when the sexes were compared separately, there was no statistically significant difference between the controls and ADHD adults. To achieve significance, the data were lumped together to include a disproportionate number of women in the controls. In addition, when individual areas of the brain were compared between controls and ADHD adults, no differences were found. It is usually possible to massage data to produce some sort of statistical result, and Zametkin et al. s study is a classic illustration. 

Since the behaviors associated with ADHD do not constitute an organic disorder but, in most cases, a manifestation of conflict between children and adults, it is unreasonable to expect that a biological cause will ever be found. Put another way, since the adults have more influence over the origins and resolutions of the problem, it is irrational to seek a biological defect in the child. Golden (1991) put it simply  

Attempts to define a biological basis for ADHD have been consistently unsuccessful. The neuroanatomy of the brain, as demonstrated by neuroimaging studies, is normal. No neuropathologic substrate has been demonstrated, (p. 36) 

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