ADDH and conduct disorder: degree of diagnostic overlap and differences among correlates.

The objective of this paper was to determine the degree of diagnostic overlap between attention deficit disorder with hyperactivity (ADDH) and conduct disorder (CD) and to see whether ADDH children show a different pattern of demographic, familial, and developmental correlates compared to CD children. The sample for this study consisted of 2,697 4- to 16-year-olds who participated in the Ontario Child Health Study. In terms of diagnostic overlap, ADDH and CD occurred together more often than by chance alone, particularly among girls. Pure groups of ADDH and CD children differed in a variety of ways. In general, ADDH children were younger and had experienced more developmental delays and less psychosocial disadvantage than the CD children. No differences were found with respect to associated impairments, a measure of severity. Children with both ADDH and CD (a mixed group) appeared to represent a true hybrid disorder rather than one diagnosis or the other. These findings support the validity of ADDH compared to CD, at least in terms of the pattern of correlates.