An examination of the relationship between movement problems and four common developmental disorders.

It has been well recognized since the days of "minimal brain dysfunction" (Clements, 1966) that various developmental disorders have a shared aetiology. Poor motor coordination has been implicated as one of the factors in these relationships. This study examines the different patterns in symptomatology of five developmental disorders, namely developmental coordination disorder (DCD), attention-deficit/hyperactivity disorder (ADHD), reading disorder (RD), oppositional defiant disorder (ODD), and conduct disorder (CD) in order to build on the genetic work from Martin, Levy, Piek, and Hay (2006) and Martin, Piek, and Hay (2006) examining the overlap of these disorders. Latent class analysis was used on questionnaire data from 1304 families from the Australian twin ADHD project (ATAP) to examine the patterns of comorbidity of the five disorders. We confirmed and added detail to the shared symptoms between DCD, ADHD, RD, and ODD, but found no links between CD symptoms and any other disorders. Despite the close link previously identified with ODD and CD, this finding suggests a different aetiology for CD.