What is the difference between the ICD and DSM?

The ICD is a core function of the World Health Organization, spelled out in its constitution and ratified by all 193 WHO member countries. The ICD has existed for more than a century, and became WHO's responsibility when it was founded in 1948 as an agency of the United Nations. Before 1980, psychiatric diagnostic systems reflected the dominant psychoanalytic ideas of the time, emphasizing the role of experience, downplaying biology.

"The American Psychiatric Association can really be credited with a revolution in psychiatric nosology with the publication of DSM-III by introducing a descriptive nosological system based on co-occurring clusters of symptoms," said WHO psychologist Geoffrey Reed, PhD.

There was very little international participation in the DSM-III, but at the time it may have been impossible to make such a big shift at the international level, he explained. As a result, DSM-III and ICD-8 (the version in effect at the time) were quite different from one another but as the descriptive phenomenological approach to diagnose mental disorders became dominant, the DSM and ICD have become very similar, partly because of collaborative agreements between the two organizations.

Still, there is widespread sentiment that it is not helpful to the field to have two separate classification systems for mental disorders. Many important distinctions between the two systems remain, Reed said:

  • The ICD is produced by a global health agency with a constitutional public health mission, while the DSM is produced by a single national professional association.

  • WHO's primary focus for the mental and behavioral disorders classification is to help countries to reduce the disease burden of mental disorders. ICD's development is global, multidisciplinary and multilingual; the primary constituency of the DSM is U.S. psychiatrists.

  • The ICD is approved by the World Health Assembly, composed of the health ministers of all 193 WHO member countries; the DSM is approved by the assembly of the American Psychiatric Association, a group much like APA's Council of Representatives.

  • The ICD is distributed as broadly as possible at a very low cost, with substantial discounts to low-income countries, and available free on the Internet; the DSM generates a very substantial portion of the American Psychiatric Association's revenue, not only from sales of the book itself, but also from related products and copyright permissions for books and scientific articles.

Will the DSM be superseded by the ICD? There is little justification for maintaining the DSM as a separate diagnostic system from the ICD in the long run, particularly given the U.S. government's substantial engagement with WHO in the area of classification systems. But, said Reed, "there would still be a role for the DSM, because it contains a lot of additional information that will never be part of the ICD. In the future, it may be viewed as an important textbook of psychiatric diagnosis rather than as the diagnostic 'Bible.'"