Professionals in psychiatry and clinical psychology rely heavily on the guidelines laid out in the Diagnostic and Statistical Manual of Mental Disorders in order to make decisions about clients’ disorder status. This American Psychiatric Association publication was an intrepid attempt to create a comprehensive nosology of psychological problems. While reaching clinical consensus is of critical importance, this current method is fraught with problems. The original inclusion of disorders was conducted in a haphazard, unsystematic and scientific manner (Spiegel, 2005, January 3). The high comorbidity rates suggest that the decision to split rather than lump disorders may have led to a large number of disorders that do not accurately represent nature. In addition, the categorical system of the DSM creates arbitrary cutoffs for whether individuals meet diagnostic criteria. Given that many disorders have been found to be continuous, rather than dichotomous, in nature (e.g. depression; Hankin et al. 2005), the emphasis on a binary system creates a system in which a number of people with only slightly subthreshold problems that are considered “non-disordered.” Although the DSM attempts to create easily operationalized behavioral criteria, Garber and Strassberg (1991) point out that for several common childhood disorders, terms like “persistent pattern,” “considerably more frequent,” and “more common” are used to determine diagnostic criteria. This language seems to rely on clinical judgment; without clearer definitions for disorders, there is considerable room for individual variation in diagnostic determination.
The NYTimes recently wrote about the next edition.

References

Garber, J., & Strassberg, Z. (1991). Construct validity: History and application to developmental psychopathology. In D. Cicchetti, & W. M. Grove (Eds.), Thinking clearly about psychology: Essays in honor of paul E. meehl, vol. 1: Matters of public interest; vol. 2: Personality and psychopathology. (pp. 219-258). Minneapolis, MN, US: University of Minnesota Press.

Hankin, B. L. , Fraley, R. C., Lahey, B. B., & Waldman, I. D. (2005). Is depression best viewed as a continuum or discrete category? A taxometric analysis of childhood and adolescent depression in a population based sample. Journal of Abnormal Psychology, 114, 96-110.

Spiegel, A. (2005, January 3). The dictionary of disorder. The New Yorker.