Is the Inattentive Type of ADHD a Separate Disorder?


Address correspondence to Stephen P. Hinshaw, Department of Psychology, Tolman Hall #1650, University of California, Berkeley, CA 94720-1650.


The contention of Milich, Balentine, and Lynam that the inattentive type of ADHD is a disorder distinct from and unrelated to the combined type bears scrutiny. After commenting on the optimal means of validating syndromes and disorders, I concur with Milich et al. that, under current definitions, the inattentive type subsumes both children who are subthreshold for the combined type and those who display sluggish cognitive tempo and underactivity. In all probability, only the latter subgroup may be distinct, in any qualitative sense, from current conceptions of ADHD. Yet with respect to a key criterion variable, cognitive processing/ neuropsychological functioning, there is currently little definitive evidence for clear differentiation. Until nosologies allow for better phenotypic differentiation, which includes broader sets of symptoms to index inatten-tiveness, research will continue to confound these two subgroups, precluding advances regarding possible genetic, psychobiologic, neuropsychologic, cognitive, familial, developmental, and treatment-related distinctions between them. Milich et al. have prompted needed research on diagnostic reformulations and external validation regarding this crucial aspect of developmental psychopathology.