Objective: To assess the validity of the DSM-IV subtypes of attention-deficit/hyperactivity disorder (ADHD).
Method: Using structured diagnostic interviews and psychometric measures of cognitive and social functioning, the authors assessed 413 children and adolescents consecutively referred to a pediatric psychopharmacology clinic since 1991.
Results: Marked psychiatric differences were found among DSM-IV subtypes of ADHD, but few differences were found in cognitive or psychosocial functioning. The greatest psychiatric differences were found between the combined-type subjects (who tended to show more impairment in multiple domains) and the other two subgroups. The inattentive patients, however, were more likely to have required extra help in school. The hyperactive-impulsive patients were not different from controls on rates of depression, Child Behavior Checklist measures of social functioning, or psychometric measures of intellectual functioning and academic achievement.
Conclusions: The results suggest that, regarding clinical features, combined-type patients have a more severe disorder than the other DSM-IV subtypes.