Affiliations: School of Psychology, Curtin University of Technology,
Perth, Western Australia | The Centre for Cerebral Palsy, Perth, Western
Australia | School of Psychiatry, University of New South Wales,
Sydney, New South Wales, Australia
Note: [] Correspondence: Jillian G. Pearsall-Jones, School of Psychology,
Curtin University of Technology, GPO Box U1987, Perth, 6845, Western Australia.
Tel.: +618 9443 0249; Fax: +618 9266 2464; E-mail:
jillian.pearsall-jones@tccp.com.au
Abstract: The high level of comorbidity between Developmental Coordination
Disorder (DCD) and Attention Deficit Hyperactivity Disorder (ADHD) suggests
that these disorders may have a shared etiology. We used a co-twin control
design to study monozygotic (MZ) twins concordant and discordant for DCD and
ADHD. In a total of 922 sets of MZ twins, 866 sets were eligible. We found
equal numbers of DCD concordant and discordant sets; more ADHD concordant than
discordant sets; nine sets in which both twins met criteria for
DCD+ADHD; 773 sets of twins did not meet criteria for
either DCD or ADHD. The only significant sex difference between groups was for
ADHD discordant sets, with more males than females. For DCD groups there were
no significant sex differences, with slightly more girls than boys affected in
both groups. There was a greater number of oxygen perfusion complications in
DCD affected than unaffected twins, suggesting that, given equal numbers of DCD
concordant and discordant sets and a similar number of DCD girls and boys, the
role of pre- and perinatal environmental factors is stronger in the etiology of
DCD than in ADHD. Factors such as placental difficulties and hypoxia have also
been related to cerebral palsy, which suggests that DCD may fall on the upper
end of a continuum of movement disorder that includes cerebral palsy. The
results suggest different etiological pathways for DCD and ADHD. Second born
twins were at greater risk for oxygen perfusion difficulties in sets concordant
for DCD, ADHD, and unaffected for either.
