Developmental Coordination Disorder (DCD) as a distinct syndrome : a conceptual and empirical investigation
Bright children who have abnormal difficulty in acquiring age-appropriate motor skills are of increasing concern to parents, teachers and health professionals. Longitudinal studies have found the condition to be associated with educational under-achievement, impaired social development and disturbed mental well-being in adult life. Now officially known as Developmental Coordination Disorder (DC D), the question of whether this condition should really be viewed as a distinct diagnostic entity is the central theme of this thesis. In the opening chapters, the history of terms used to signify 'clumsiness' of movement is reviewed and the different implications of treating such behaviour as a symptom or syndrome is considered. Discussion then moves to the overlap between DCD and other childhood conditions and the question of how these should be conceptualised. Five studies comprising the empirical component of the thesis employed a variety of methodologies. Two questionnaire-based studies showed that in this area, neither consensus on terms nor equitable service provision has yet been achieved. A third, retrospective study, searched for evidence of sub-types within a large sample of DCD children, successfully replicating some of the cluster groups reported by others. In a final, prospective study, a two-stage identification process was followed by 'blind' assessment of boys with DCD, Asperger Syndrome or Joint Hyper-mobility Syndrome. Novel to this area was the inclusion of experimental measures, including dual-task performance, in which motor and cognitive tasks were combined. The results showed that although the group with AS were significantly poorer on ball skills than those with OCD, the general nature of motor difficulties was not systematically constrained by diagnosis. Together, these studies support the thesis that DCD exists as a separable syndrome, but bear less decisively on the existence of subtypes. A series of real-life case studies illustrates the problems associated with differential diagnosis and the implications for appropriate intervention.