56 Neurodevelopmental Disorders
second birthday (see also Rett syndrome in  the section “Differential Diagnosis” for this
disorder).
First symptoms of autism spectrum disorder frequently involve delayed language de-
velopment, often accompanied by lack of social interest or unusual social interactions (e.g.,
pulling individuals by the hand without any a ttempt to look at them ), odd play patterns
(e.g., carrying toys around but never pl aying with them), and unusual communication
patterns (e.g., knowing the alphabet but not responding to own name). Deafness may be
suspected but is typically ruled out. During the second year, odd and repetitive behaviors
and the absence of typical play become more apparent. Since many typically developing
young children have strong preferences and en joy repetition (e.g., eating the same foods,
watching the same vide o multiple times), dist inguishing restricted and repetitive behav-
iors that are diagnostic of autism spectrum disorder can be difficult in preschoolers. The
clinical distinction is based on the type, freq uency, and intensity of the behavior (e.g., a
child who daily lines up objects for hours an d is very distressed if any item is moved).
Autism spectrum disorder is not a degenera tive disorder, and it is typical for learning
and compensation to continue throughout life.  Symptoms are often most marked in early
childhood and early school years, with deve lopmental gains typical in later childhood in
at least some areas (e.g., increa sed interest in social interact ion). A small proportion of in-
dividuals deteriorate behaviorally during adolescence, whereas most others improve.
Only a minority of individuals with autism  spectrum disorder live and work indepen-
dently in adulthood; those who do  tend to have superior lang uage and intellectual abilities