5Introduction
The creation  of the fifth edition of Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) was a massive undertaking that involv ed hundreds of peop le working toward a
common goal over a 12-year process. Much thought and deliberation were involved in
evaluating the diagnostic criter ia, considering the organization of every aspect of the man-
ual, and creating new features believed to be mo st useful to clinicians. All of these efforts
were directed toward the goal of enhancing th e clinical usefulness of DSM-5 as a guide in
the diagnosis of mental disorders.
Reliable diagnoses are essential for guidin g treatment recommendations, identifying
prevalence rates for mental health service pl anning, identifying patient groups for clinical
and basic research, and documenting importan t public health information such as mor-
bidity and mortality rates. As the understand ing of mental disorders and their treatments
has evolved, medical, scientific, and clinical professionals have focused on the character-
istics of specific disorders and their im plications for treatment and research. 
While DSM has been the cornerstone of substant ial progress in reliability, it has been well
recognized by both the American Psychiatric Association (APA) and the broad scientific com-
munity working on mental diso rders that past science was no t mature enough to yield fully
validated diagnoses—that is, to provide consistent, strong, and objective scientific validators
of individual DSM disorders. The science of mental disorders continues to evolve. However,
the last two decades since DSM-IV was released  have seen real and durable progress in such
areas as cognitive neuroscience , brain imaging, epidemiology, and genetics. The DSM-5 Task
Force overseeing the new edition recognized that research advances will require careful, iter-
ative changes if DSM is to maintain its place as  the touchstone classifi cation of mental disor-