Letters Response

World Health Organization responds to Fiona Godlee and Ray Moynihan

BMJ 2011; 342 doi: https://doi.org/10.1136/bmj.d3830 (Published 20 June 2011) Cite this as: BMJ 2011;342:d3830
  1. Geoffrey M Reed, senior project officer, revision of ICD-10 Mental and Behavioural Disorders1,
  2. Tarun Dua, medical officer, evidence, research and action on mental and brain disorders1,
  3. Shekhar Saxena, director1
  1. 1Department of Mental Health and Substance Abuse (MSD/MER), World Health Organization, CH-1211 Geneva, Switzerland
  1. reedg{at}who.int

In her editor’s choice in the print issue of 14 May Godlee asks: “Who should define disease?”1 This question was answered by international treaty in 1948, when the World Health Organization was founded as a specialised agency of the United Nations. The WHO has unique authority to establish global health standards and secure international agreement on defining diseases. Among the core functions in its constitution are responsibility for international definitions and nomenclatures of disease, and standardising diagnostic procedures.2 The WHO’s 193 member states have agreed to use the International Classification of Diseases (ICD) as a basis for reporting health information that is usable and comparable across countries. The World Health Assembly—comprising the health ministers of all member states—has directed the WHO to revise ICD-10, a process expected to lead to the completion of ICD-11 in 2014.

The classification of mental and behavioural disorders is particularly sensitive in terms of creating and defining disease categories,1 so the WHO has implemented a systematic process for evaluating and using evidence as part of the ICD-11 development process, including formative and evaluative field testing. Existing categories and definitions of mental disorders should be changed through a transparent, international, multidisciplinary, and multilingual process that entails the direct participation of a broad range of stakeholders and is as free as possible from conflicts of interest. As Moynihan argues,3 a truly multilateral process of disease definition cannot be legitimately managed by a single professional organisation representing a single health discipline in a single country with a substantial commercial investment in its products.

The WHO is concerned about the proliferation of diagnoses of mental disorders. The use of classification systems by professional societies to mark out professional turf may lead to redundancy and clinically unimportant distinctions in disease definitions—which is less likely in the context of a global public health agency. Even so, issues of threshold are complex because the pathophysiology underlying mental disorders cannot be assessed directly and many symptoms of psychopathology are continuous with normal phenomena. Appropriate use of the ICD would discourage reification of questionable entities because it contains specific provisions for identifying phenomena that are important to treatment and clinical management but are not in themselves disorders.

Identifying a phenomenon as an important topic for research does not automatically mean that it should be defined as a disease. Evidence on validity and clinical importance is required, as well as consideration of the public health justification for inclusion. Disease classifications have not proved to be the best organising framework for research on basic mechanisms,4 but a classification’s usefulness for research should not be confused with its validity for other purposes. Evidence evaluation for disease definitions should focus on their different purposes and target users, using a broader range of methods appropriate to evaluating clinical utility and public health outcomes.

The argument for definition of new conditions is often implicitly based on the goal of obtaining reimbursement to treat them, if not to expand markets for pharmaceutical products. However, healthcare financing and reimbursement policy are separate issues from disease definition.5 To conflate them is not helpful in reducing the global burden of disease. To include a condition in a disease classification does not automatically mean that treatment should be provided or that governments or private insurance should pay for it. Failure to separate diagnosis from health policy contributes to over-treatment but also to under-treatment of serious mental disorders and misdirection of mental health care resources.


Cite this as: BMJ 2011;342:d3830


  • Competing interests: None declared.


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