Motor flexibility problems as a marker for genetic susceptibility to attention-deficit/hyperactivity disorder.
BACKGROUND
Since many children with attention-deficit/hyperactivity disorder (ADHD) have fine visuomotor problems that are already evident at a young age, motor dysfunctioning is investigated in family-genetic perspective. We hypothesized that if fine motor problems may be a marker for genetic susceptibility to ADHD, nonaffected siblings of ADHD probands would experience motor problems similar to those of their ADHD siblings.


METHODS
Twenty-five carefully phenotyped ADHD probands with a family history of ADHD, their nonaffected siblings (n = 25), and 48 normal control subjects (aged 6 to 17) completed a motor fluency task and a motor flexibility task. The motor fluency task involved completion of a familiar, automatized trajectory, whereas the motor flexibility task required continuous adjustment of movement to complete an unpredictable random trajectory.


RESULTS
On the motor fluency task, the performance of the nonaffected children was significantly better than that of the ADHD probands; strikingly, on the motor flexibility task, they performed as well as their ADHD siblings.


CONCLUSIONS
Nonaffected siblings experience complex motor problems similar to their ADHD siblings but only in nonautomatized movements that require controlled processing. The results suggest that higher-order controlled motor deficits in ADHD may be associated with genetic susceptibility for ADHD.
Academic Center for Child and Adolescent Psychiatry Oost-Nederland, University Medical Center St. Radboud, Reinier Postlaan 12, 6525 GC Nijmegen, The Netherlands. dorine.slaats@skjpon.nl
Dorine
D
Slaats-Willemse
Leo
L
de Sonneville
Hanna
H
Swaab-Barneveld
Jan
J
Buitelaar
D000293:Adolescent; D000704:Analysis of Variance; D001288:Attention; D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications*; D015415:Biomarkers; D016022:Case-Control Studies; D002648:Child; D005192:Family Health; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007360:Intelligence; D008297:Male; D019957:Motor Skills Disorders / Q000209:etiology / Q000235:genetics*; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D010641:Phenotype; D018583:Pliability; D011597:Psychomotor Performance / Q000502:physiology*
D015415:Biomarkers