76 Neurodevelopmental Disorders
dinated movements continue th rough adolescence in an esti mated 50%–70% of children.
Onset is in early childhood. Delayed motor mile stones may be the first signs, or the disor-
der is first recognized when the child attempts  tasks such as holding a knife and fork, but-
toning clothes, or playing ball games. In middle childhood, there are difficulties with
motor aspects of assembling puzzles, building  models, playing ball, and handwriting, as
well as with organizing belongings, when mo tor sequencing and co ordination are re-
quired. In early adulthood, there is continuing difficulty in learning new tasks involving
complex/automatic motor skills, including drivin g and using tools. Inability to take notes
and handwrite quickly may affect performance in the workplace. Co-occurrence with
other disorders (see the sectio n “Comorbidity” for this disorder) has an additional impact
on presentation, course, and outcome.
Risk and Prognostic Factors 
Environmental. Developmental coordination disorder  is more common following pre-
natal exposure to alcohol and in pr eterm and low-birth-weight children.
Genetic and physiological. Impairments in underlying neurodevelopmental processes—
particularly in visual-motor sk ills, both in visual-motor perception and spatial mentalizing—
have been found and affect the ability to make rapid motoric adjustments as the complexity of
the required movements increases. Cerebellar dysfunction has been proposed, but the neural
basis of developmental coordination disorder remains unclear. Because of the co-occurrence of
developmental coordination disorder with atte ntion-deficit/hyperactiv ity disorder (ADHD),
specific learning disabilities, and autism spectr um disorder, shared genetic effect has been pro-
posed. However, consistent co-occurrence in twins appears only in severe cases.