Two visions for understanding illness: DSM and the International Classification of Diseases

The DSM-5 is not the only system of classification of mental illness. Image from shutterstock.com

The new Diagnostic and Statistical Manual (DSM-5) is the latest instalment in the long-running saga over the classification, nature and dimensions of mental illness. But it’s not the only system of classification of mental illness.

Since 1948, the World Health Organization has produced a section on mental diagnoses in its International Classification of Diseases (ICD). To understand why the DSM is such a controversial document, we need a sense of its historical relationship to the ICD.

Initial harmony

Between 1948 and 1965, the World Health Organisation produced three editions of the International Classification of Diseases. The release of ICD-6 in 1948 prompted the American Psychiatric Association (APA) to produce DSM-I in 1952. The American Psychiatric Association had lofty ambitions for its new manual.

Following the Second World War, the American Psychiatric Association was taken over by a group of young practitioners influenced by the Freudian model, with its emphasis upon neurotic illnesses. They met with some resistance from older psychiatrists, but their promise to extend psychiatry’s reach out of the mental hospitals and into society at large guaranteed them a 20-year dominance of the organisation.

Using ICD-6 as the foundation, they built their own classification system that served the interests of their profession. Between the ICD-6 and ICD-8, the World Health Organization’s classification was more or less harmonised with the DSM. And ICD-8 (1965) was very close to DSM-II (1968) in organisation, categories and description.

DSM’s misstep

To its detriment, however, DSM-II included homosexuality as a psychiatric condition. The gay liberation movement had emerged alongside the wider civil rights and women’s liberation movements, and forcefully challenged the APA’s pathologisation of homosexuality.

Following protests in the early 1970s, US psychiatrist and chair of DSM-III’s task force Robert Spitzer was given the task of defusing the situation. He redefined mental illness to exclude homosexuality from the DSM, replacing it with “sexual orientation disturbance”, which was supposedly experienced by those uncomfortable with their sexuality.

Although this was retrospectively celebrated as a milestone of psychiatric progressiveness, at the time many argued this decision was unscientific. How could something that had long been regarded as a disease be removed from a classificatory system as a result of political pressure?

Change of direction

Other criticisms were levelled against the APA on the back of this move. Insurance companies insisted they would only pay to treat “real” diseases, while an anti-psychiatry movement had become almost mainstream in many US universities. Something had to be done.

Spitzer was a long-term critic of post-war Freudian psychiatry and, along with a few like-minded colleagues, was deeply influenced by Emil Kraepelin, who had developed a method of descriptive psychiatry in the late 1890s.

Kraepelin’s system had no underlying theory of causation. Instead, he focused a detailed picture of the symptoms experienced by each of his patients. Collating these, he identified the twin-pillars of the psychoses: dementia praecox (later renamed schizophrenia) and manic depression (rebranded as bipolar).

Kraepelin’s method was not to many people’s liking in the early 1970s. But for Spitzer and his allies, it was a means to the end of transforming psychiatry. The psychobabble of the Freudian couch would be replaced by Kraepelin-style lists of symptoms that had to be observed before a categorical diagnosis could be made.

A transformation

The neo-Kraepelinians transformed the DSM to fit this model. DSM-III (1980) was, therefore, a radical departure from previous incarnations of the DSM and the ICD. The WHO responded by incorporating DSM-III’s innovations into ICD-10.

Nevertheless, there were significant differences between the two classifications. Nomenclature, diagnostic criteria and categories did not map one-to-one. What’s more, the DSM remained culture-bound and unable to cope with the complexities of gender and ethnicity in a multicultural world.

Harmonisation between the ICD and the DSM has remained an expressed goal of both the APA and the WHO. Currently, the APA is trumpeting the fact that ICD-11 will be very close to DSM-5. Whether this happens remains to be seen. And whether it is desirable is questionable.

Divergent aims

The DSM and the ICD serve similar but distinct purposes. While both can broadly be described as classifications that aid the collection and analysis of morbidity data, there has always been considerable scope to the ambitions of the DSM.

The ICD can be used for research while providing a tool for understanding patterns of mental illnesses. It may even contribute to diagnosis. But the DSM clearly wants to shape the wider practice of psychiatry.

There is no ICD equivalent of the DSM casebook, which shows how the DSM can be used in diagnosis and treatment. Neither is the ICD implicated in the jostling between pharmaceutical companies, the health insurance industry and the psychiatry profession, as each haggles with the other over the existence or the extension of particular illness categories.

Nor is the ICD a cash-cow for the WHO, unlike the DSM, which is a highly profitable enterprise. Indeed, the DSM is most certainly not disinterested.

International impact

For the majority of psychiatric practitioners outside of the United States, the DSM is one tool among many. Outside the US, it doesn’t possess the same power or authority. In Australia, for example, psychiatrists might be trained using the diagnostic criteria of the DSM to help them pass their exams, but in general they rely on clinical literature that is more detailed and, above all, relevant to their day-to-day practice.

Equally, the diagnoses of most clinicians, in the US and elsewhere, is coded using the ICD classification, which remains the principal means of statistically detailing the incidence of categories of mental illnesses.

The DSM-5 will probably be the most controversial book of 2013, provoking discussions about the reality, or otherwise, of particular diagnoses. But we shouldn’t get carried away with its influence over psychiatry worldwide. Outside of the US, psychiatrists are more concerned, on the one hand, with the wider clinical literature, and, on the other, using the ICD as a superior cross-cultural classification.