xlii Preface
•Representation of developmental issues related to diagnosis.  The change in chapter
organization better reflects a lifespan approach, with disorders more frequently diag-
nosed in childhood (e.g., neurodevelopmental  disorders) at the beginning of the man-
ual and disorders more applicable to olde r adulthood (e.g., neurocognitive disorders)
at the end of the manual. Also, within the text, subheadings on development and course
provide descriptions of how disorder pr esentations may change across the lifespan.
Age-related factors specific to diagnosis (e.g., symptom presentation and prevalence
differences in certain age groups) are also included in the text. For added emphasis,
these age-related factors have been added to  the criteria themselves where applicable
(e.g., in the criteria sets for insomnia di sorder and posttraumati c stress disorder, spe-
cific criteria describe how symptoms might be expressed in children). Likewise, gender
and cultural issues have been integrat ed into the disorders where applicable.
•Integration of scientific findings from th e latest research in genetics and neuroimag-
ing. The revised chapter structure was informed by recent research in neuroscience and
by emerging genetic linkages between diag nostic groups. Genetic and physiological
risk factors, prognostic indicators, and so me putative diagnostic markers are high-
lighted in the text. This new structure shoul d improve clinicians’ ability to identify di-
agnoses in a disorder spectrum based on common neurocircuitry, genetic vulnerability,
and environmental exposures. 
•Consolidation of autistic disorder, Asperg er’s disorder, and pervasive developmen-
tal disorder into autism spectrum disorder.  Symptoms of these disorders represent a
single continuum of mild to severe impair ments in the two domains of social commu-
nication and restrictive repetitive behaviors/ interests rather than being distinct disor-