TEST OF 4 HYPOTHESES FOR THE COMORBIDITY OF ATTENTION-DEFICIT HYPERACTIVITY DISORDER AND CONDUCT DISORDER

Objective: To study the basis of the comorbidity of two common psychia tric disorders of childhood: attention-deficit hyperactivity disorder (ADHD) and conduct disorder (CD). Method: Subjects were 45 boys (aged 7 to 11 years) with either ADHD, CD, or ADHD+CD and 16 normal control children (NC) studied by means of a 2 (ADHD versus no ADHD) x 2 (CD ve rsus no CD) design. We (1) tested whether similar or different pattern s of cognitive, developmental risk, and psychosocial factors character ize the ''pure'' forms of the two disorders (i.e., ADHD and CD), and ( 2) compared the profile of the comorbid group (ADHD+CD) with those of the two pure groups. Results: The ADHD group was significantly impaire d on cognitive measures (inhibitory control and response alteration) a nd had greater delay in development and greater reading problems compa red with CD and NC children; the CD group was exposed to significantly greater environmental adversity and had more severe problems in arith metic than the ADHD and NC groups. The ADHD+CD group was similar to th e ADHD group on cognitive, developmental, and reading measures and sim ilar to the CD group on psychosocial and arithmetic measures. Conclusi ons: These results support the distinctiveness of ADHD and CD and the hypothesis that the comorbid condition of ADHD+CD is a hybrid of pure ADHD and pure CD.