Patterns of comorbidity associated with subtypes of attention-deficit/hyperactivity disorder among 6- to 12-year-old children.

OBJECTIVE: To study externalizing and internalizing comorbidity patterns in 6- to 12-year-old children with attention-deficit/hyperactivity disorder (ADHD) combined subtype (n = 27), ADHD inattentive subtype (n = 26), and a normal control group (n = 33).
METHOD: Children were assigned to groups on the basis of results of a parent structured interview, which reflected DSM-IV diagnostic criteria, and teacher ratings of ADHD symptoms. Comorbid problems were assessed via parent and child structured interviews and parent and teacher behavior ratings.
RESULTS: Logistic regression analyses and multivariate analyses of covariance revealed that (1) children in the ADHD combined group were significantly more likely to have a diagnosis of oppositional defiant disorder and conduct disorder and had significantly higher scores on parent and teacher ratings of externalizing problems than children in the ADHD inattentive and control groups, (2) children in the ADHD combined and ADHD inattentive groups had significantly higher scores on parent and teacher ratings of internalizing problems than children in the control group, and (3) children in the clinical groups did not differ with regard to internalizing disorders.
CONCLUSIONS: The results from this study indicate that a significant comorbidity exists between ADHD combined and oppositional defiant disorder/conduct disorder. Contrary to previous studies that were conducted using DSM-III diagnostic criteria for ADHD, no differences were found between ADHD combined and ADHD inattentive subtypes regarding internalizing disorders.