6 Introduction
examination of the range of symptoms present, DSM can serve clinicians as a guide to identify
the most prominent symptoms that should be assessed when diagnosing a disorder. Although
some mental disorders may have well-defined  boundaries around symptom clusters, scien-
tific evidence now places many, if not most, disorders on a spectrum with closely related dis-
orders that have shared symptoms, shared genetic and environmental risk factors, and
possibly shared neural substrates (perhaps most  strongly established for a subset of anxiety
disorders by neuroimaging and animal models). In short, we have come to recognize that the
boundaries between disorders are more  porous than originally perceived.
Many health profession and educational groups have been  involved in the development
and testing of DSM-5, including physicians, psychologists, social workers, nurses, counselors,
epidemiologists, statisticians, neuroscientists, and neuropsychologists. Finally, patients, fam-
ilies, lawyers, consumer organizations, and advoca cy groups have all participated in revising
DSM-5 by providing feedback on the mental di sorders described in this volume. Their moni-
toring of the descriptions and explanatory text  is essential to improve  understanding, reduce
stigma, and advance the treatment and eventual cures for these conditions.
A Brief History
The APA first published a predecessor of DSM in 1844, as a statistical classification of in-
stitutionalized mental patients. It was designed to improve co mmunication about the
types of patients cared for in these hospitals.  This forerunner to DSM also was used as a
component of the full U.S. census. After World War II, DSM evolved through four major
editions into a diagnostic classification system for psychiatrists, other physicians, and
other mental health professionals that descri bed the essential features of the full range of