Developmental coordination disorder: a review of research on subtypes and comorbidities
Introduction
Since Developmental Coordination Disorder (DCD) was first listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM) it has received a great deal of attention from researchers in areas such as education, psychology, kinesiology, and physical and occupational therapy. In recent years, motor journals have dedicated complete issues to the disorder (Barnett, Kooistra, & Henderson, 1998; Beek & van Wieringen, 2001; Henderson, 1994). But, despite this surge of interest, the etiology and prognosis of DCD are still unclear. Children diagnosed with DCD may show a variety of symptoms, and their specific needs, as well as their prognosis will differ accordingly. If we want to understand the etiology and prognosis of DCD, we need to have a better understanding of its nature. This requires an awareness of the existence of subtypes and comorbidities.
This review presents a summary of the findings on differences between children with DCD and controls. The main focus of the review, however, is on research on subtypes and comorbidities. The PsycINFO and Medline databases were searched for relevant articles, using keywords such as: Developmental Coordination Disorder, Attention Deficits, Hyperactivity, Reading Disability, Dyslexia, Specific Language Impairment, Comorbidity, and Subtypes. Publications that were referenced in these articles were added, as well as other publications known to the author.
Section snippets
What is DCD?
The fact that we still understand so little about the etiology and prognosis of DCD is partly due to inconsistencies in diagnostic criteria. These inconsistencies have led to widely diverging samples, which makes it hard to reach an overall conclusion about the findings. According to the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1994), Developmental Coordination Disorder is a marked impairment in the development of motor
Research on subtypes and comorbidities
Thus far, research on subtypes and comorbidities has developed along more or less separate lines. Studies on subtypes of DCD try to find differences among the children in their performance on a series of sensorimotor measures. Typically, these studies do not look at comobidity phenomena. Comorbidity studies, on the other hand, look at relationships between DCD and other developmental disabilities, but typically do not distinguish among the children with DCD. The following sections present a
ABD: The atypical brain development hypothesis
According to Kaplan et al. (1998), brain imaging techniques have generally failed to support the idea that unique brain areas are associated with individual developmental disorders. Dyslexia, for example, has been linked to deficits in the left temporal-parietal area, but when other brain areas are examined, atypical brain development is visible in both hemispheres and in cortical as well as subcortical areas (Riccio & Hynd, 1996). Similarly, atypical brain development in ADHD is not limited to
Conclusions
There is more and more evidence indicating that DCD is not a uniform disorder. Rather, there appear to be different subtypes of disabilities, either pure or comorbid, with different causes, different treatment requirements and different outcomes. A definition of subtypes is important, as it will increase our insights into the specific problems a child experiences, and improve the diagnosis and treatment of children with these disabilities.
Although some subtype studies have been conducted, very
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