Global launch of the ICD-11 Clinical Descriptions and Diagnostic Requirements (CDDR)
D. Kestel is the Director of the WHO Department of Mental Health and Substance Use. The authors alone are responsible for the views expressed in this paper, that do not necessarily represent the views, decisions or policies of the WHO or the other institutions with which they are affiliated.
The ICD-11, the first major revision of the ICD in three decades, was approved by the 72nd World Health Assembly in May 2019, and came into effect as a basis for reporting of health statistics by World Health Organization (WHO) member states in January 2022. Countries around the world are in various stages of implementing the ICD-11 in their clinical and health information systems, a process that will continue for the next several years.
The WHO has now taken a major step towards the implementation of the ICD-11 in mental health systems by publishing the Clinical Descriptions and Diagnostic Requirements for ICD-11 Mental, Behavioural and Neurodevelopmental Disorders (CDDR)1.
The CDDR are designed as a comprehensive diagnostic manual that will support mental health and other health professionals in accurately diagnosing mental disorders in health care settings across the world. They provide consistent, clinically useful information for all diagnostic categories in the ICD-11 chapter on mental, behavioural and neurodevelopmental disorders. This information includes the features that clinicians can expect to see in all cases of the disorder (essential features), their boundaries with normality (threshold) and other conditions (differential diagnosis), and features related to course, developmental stage, gender and culture. Although a diagnostic manual had been published for the ICD-10, the CDDR represent a substantial expansion and improvement in the consistency of information provided, the integration of systematic information related to developmental stage, gender and culture, and more careful attention to differential diagnosis2, in addition to being based on current research and best practices.
For the WHO Department of Mental Health and Substance Use, a central goal in developing the ICD-11 CDDR was to provide a better tool for reducing the global burden of mental disorders. Based on this goal, we focused explicitly on clinical utility and global applicability – in addition to validity – in the CDDR's development3. An accurate diagnosis is often the first critical step towards receiving appropriate care and treatment. A more clinically useful diagnostic manual that is more applicable in settings across the world is more likely to be implemented systematically, supporting both the earlier identification of those who need care and the selection of effective treatment. In turn, this will improve the quality of health data aggregated from clinical encounters that are used to guide policy and allocate resources at facility, system, national and global levels.
To develop the CDDR, the Department appointed sixteen expert working groups in different areas, ensuring through their composition a multidisciplinary process that represented all WHO regions, including a substantial proportion of individuals from low- and middle-income countries. In developing proposals for the ICD-11, these working groups conducted rigorous reviews of the evidence, including work done as a part of the development of the DSM-5.
Further, proposed diagnostic requirements for the ICD-11 were extensively tested in a systematic program of field studies. The Global Clinical Practice Network (GCPN) was set up to enable the participation of clinicians in the development of the CDDR, and now consists of more than 19,000 mental health and primary care professionals from 165 countries. GCPN members participated in 20 Internet-based field studies to test the CDDR, each conducted in up to six languages3, 4. The CDDR were also tested among patients in clinical settings in 15 countries, representing all WHO regions and nearly 50% of the world's population. These studies documented broad improvements in reliability and clinical utility when clinicians used the ICD-11 CDDR as compared to the equivalent diagnostic guidance for ICD-10.
The ICD-11 and the CDDR incorporate important innovations. These include new disorder categories that describe populations with clinically important and distinctive features and specific treatment needs, substantially contributing to an expansion of related research and a significant increase in the availability of appropriate services5. Other categories have been eliminated due to their lack of validity. The ICD-11 and the CDDR have made a significant movement toward dimensional conceptualizations of mental disorders, especially in psychotic and personality disorders6.
- The CDDR support universal health coverage by describing in replicable, clinically useful, and globally applicable terms the conditions that provide a framework for treatment eligibility and selection.
- The CDDR support human rights, for example by emphasizing current status and treatment needs rather than lifelong labeling for psychotic disorders, in ways that are more consistent with recovery-based approaches.
- The CDDR are based on substantial advances in evidence-based practice since the publication of the ICD-10.
- The CDDR are based on a life-course approach, describing manifestations of mental disorders in early and middle childhood, adolescence, and older adulthood.
- As described above, the Department of Mental Health and Substance Use adopted a multi-sectoral approach to developing the CDDR.
- The CDDR support empowerment of persons with mental disorders and psychosocial disabilities by systematically incorporating service user perspectives8.
In order to implement the ICD-11 and the CDDR, there is a huge need for workforce capacity-building for both specialist and non-specialist providers of services. The implementation of the ICD-11 also represents the most important opportunity in a generation to reform the diagnostic process, incorporating the needs and perspectives of those who receive our care8. The WHO will need the collaboration and support of member states, professional societies (importantly including the World Psychiatric Association), WHO Collaborating Centres, academic institutions, non-governmental organizations, civil society and service user organizations to ensure an implementation of the ICD-11 that fulfils its potential. The CDDR should be systematically integrated into training programs for mental health and primary care professionals, and a range of more specialized materials should be developed for this purpose9.
The CDDR are the product of more than 15 years of collaborative work led by the WHO Department of Mental Health and Substance Use within the context of the overall development of the ICD-11. Hundreds of experts and thousands of clinicians from around the world were involved in developing and testing the CDDR as part of the most international, multilingual, multidisciplinary and participative revision process ever implemented for a classification of mental disorders.
With the publication of the CDDR, health professionals have a better tool for identifying mental health conditions; WHO member states have a better tool for reducing the disease burden associated with mental disorders; and people who need mental health services have a greater likelihood of receiving the care they need.
