Taxonomic examination of ADHD and conduct problem comorbidity in elementary school children using cluster analyses

Cluster analysis was used to investigate the classification of comorbid Attention Deficit Hyperactivity Disorder (ADHD) + Conduct Problems (CP). Teachers rated 1394 elementary school children on symptoms of inattention, hyperactivity/impulsivity, opposition, and conduct problems using the ADS-IV behavior-rating scale. Results suggested that a seven-cluster solution, including two distinct comorbid clusters, was the most appropriate method of classifying children according to behavioral symptoms. A one-way MANOVA showed that overall cluster profiles differed significantly from each other, whereas one-way ANOVAs indicated that clusters differed on age and symptom scores. Chi-square analyses indicated that clusters differed on gender. Post hoc analyses and effect sizes calculations revealed that the comorbid clusters differed from each other and from their single-disorder counterparts on some variables, but not on all. These results provide support for an additive conceptualisation of ADHD + CP.