Identification of AD/HD subtypes using laboratory-based measures: a cluster analysis.

The current investigation used laboratory-based measures of inattention, impulsivity, and activity level to identify subgroups of children with attention-deficit/hyperactivity disorder (AD/HD). Data derived from solid state actigraphs and a continuous performance test (CPT) were obtained from a clinically referred sample and submitted to a cluster analysis. These empirically derived groups were then evaluated for clinical relevance and subsequently validated by parent and teacher ratings and tests of intellectual functioning and academic achievement. Four distinct subgroups emerged: Hyperactive-inattentive (HYP-IN), impulsive-inattentive (IMP-IN), inattentive only, and hyperactive only. The HYP-IN group was impaired on measures of intellectual functioning and academic achievement relative to the other three groups. In contrast, the IMP-IN group was generally rated as more aggressive, although this difference was not statistically significant for all measures. The data suggest that the augmentation of clinical descriptors with laboratory-based data may be an effective strategy by which to categorize diagnostic subgroups of AD/HD.