Experimental cross-validation of DSM-IV types of attention-deficit/hyperactivity disorder

Objective: To examine the discriminant validity of DSM-IV attention-deficit/hyperactivity disorder (ADHD) types by testing the hypothesis that types are associated with specific kinds of functional impairment and to compare overlap of DSM-IV and DSM-III-R ADHD. Method: Consecutive referrals (n = 692) to a pediatric subspecialty clinic for ADHD were classified into 1 of each of the 3 DSM-IV types of ADHD using parent and teacher checklist ratings of ADHD symptoms. The resulting types were compared on clinical correlates and on whether the children also met criteria for DSM-III-R ADHD. Results: The validity of DSM-IV types was supported by dimension-specific impairment and other distinct correlates. Academic problems aggregated in the 2 types defined by extreme inattention, and externalizing problems aggregated in the 2 types defined by extreme hyperactivity. Conclusion: DSM-IV appeared superior to DSM-III-R in subcategorical homogeneity and in exhaustiveness (ability to classify all apparent cases).