There is a natural human predilection to categorize and classify for simplifying and organizing the wide range of observable phenomena and experiences that one is confronted with, thus facilitating both their understanding and their predictability. The current system for the diagnosis of mental disorders, the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) (American Psychiatric Association, 1994), is just the latest example from the long and colorful history of psy-chiatric classification. Although there was a more recent text revi-sion, DSM-IV-TR (American Psychiatric Association, 2000), we will refer to DSM-IV as the “current’’ version since DSM-IV-TR primarily differs with respect to the textual descriptions of the disorders. The classification, diagnostic terms and virtually all of the diagnostic criteria are identical (First and Pincus, 2002).
Perhaps the most important goal of a psychiatric classification is to allow mental health practitioners and researchers to commu-nicate more effectively with each other by establishing a conven-ient shorthand for describing the mental disorders that they see (First, 1992). For example, saying to a colleague that a patient has major depressive disorder can convey a great deal of information in only a few words. First of all, it indicates that depressed mood or loss of interest is a central aspect of the presenting problem and that the depression is not the kind of “normal’’ mood fluctuation that lasts for only a few days but rather that it persists every day for an extended period of time, for at least 2 weeks. Furthermore, one can expect to find a number of additional symptoms occur-ring at the same time, like suicidal ideation and changes in appe-tite, sleep, energy and psychomotor activity. Finally, information is also communicated about what is not to be found in this patient – specifically, that the depression is not caused by the direct phys-iological effects of alcohol, other drugs, medications, or a general medical condition; that substance use and general medical condi-tions have been ruled out as etiological factors; and that there is no history of schizophrenia or manic or hypomanic episodes.
DSM-IV also facilitates the identification and management of mental disorders in both clinical and research settings. Most of the DSM-IV diagnostic labels provide considerable and important predictive power. For example, making a diagnosis of bipolar disor-der suggests the choice of treatment options (e.g., mood stabilizers), that a certain course may be likely (e.g., recurrent and episodic), and that there is an increased prevalence of this disorder in family mem-bers. By defining more or less homogeneous groups of individu-als for study, DSM-IV can also further efforts to understand theetiology of mental disorders. The classifications of the manual have been a reflection of, and a major contribution to, the development of an empirical science of psychiatry. DSM-IV also plays an important role in education. In its organization of disorders into major classes, the system offers a structure for teaching phenomenology and dif-ferential diagnosis. DSM-IV is also useful in psychoeducation by showing patients that their pattern of symptoms is not mysterious and unique but rather has been identified and studied in others.