What is New in the ICD-11 on Mental, Behavioural or Neurodevelopmental Disorders

Structure of Chapter 06

The hierarchy of Chapter 06 comprises:

1st level - Broad category of disease/disorder type
2nd level - Specific disease/disorder type
3rd level - Further specificity of disease/disorder type

The Rationale for Chapter 06

Since the time of the Advisory Group’s initial appointment in 2007, the overall linear structure of the proposed mental, behavioural, or neurodevelopmental disorders chapter for ICD–11 has been the subject of substantive and comprehensive discussions by the Topic Disorders Advisory Group for Mental Health, as well as extensive interactions with the American Psychiatric Association concerning the just-published Fifth Edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) (1), from the time of the Advisory Group’s initial appointment in 2007.

The architecture of diagnostic classification of mental and behavioural disorders is an issue that has received substantial attention throughout the revision (e.g. 2-4). One goal of the ICD–11 is to reflect current scientific evidence regarding the relationships among disorders (5) rather than antiquated concepts such as ‘neurosis’, which have poor construct and predictive validity. In addition, a major goal of the WHO Department of Mental Health and Substance Abuse for the current revision is to improve the clinical utility of this part of the ICD–11 (6, 7). Because the ICD–11 uses a different coding structure that is not based on a decimal numbering system, such that it can accommodate a larger number of blocks or groupings within the chapter, it presented an important opportunity to bring the classification more in line with current research and clinical practice in terms of how groupings of disorders are represented.

Three streams of work provide the rationale and evidence for the linear structure of Mental and Behavioural Disorders in the ICD–11.

Evidence Reviews by Working Groups for ICD–11 Mental, behavioural, or neurodevelopmental disorders

The first workstream relates to the outcome of evidence reviews by the 14 working groups reporting to the Advisory Group, each of which had multiple face-to-face meetings over at least 2 years. They asked the Working Groups to review the available scientific evidence and other information about the clinical application of classifications in various settings throughout the world and provide evidence and a rationale for its groupings and the content and arrangement of categories within them. This work resulted in manuscripts describing the rationale for most groupings of disorders that have been published in or submitted to peer-reviewed journals (e.g. 8-15). Space does not permit detailing the rationale and evidence base for each structural change here. Still, it can provide this information related to any specific decision on request based on the material generated by the Working Groups.

Formative Field Studies on Clinical Utility of the Linear Structure

The second stream of work relevant to the linear structure of Mental and Behavioural Disorders focused on clinical utility and is represented by two formative field studies undertaken by the WHO and the Field Studies Coordination Group reporting to the Advisory Group (16, 17). The purpose of these studies was to examine the conceptualisations held by mental health professionals around the world of the relationships among mental disorders to inform decisions about the classification structure. From a clinical utility perspective, particularly to improve the interface between health information and clinical practice, the most important and desirable features of a classification’s organisation are that (a) it helps clinicians find the categories that most accurately describe the patients they encounter as quickly, easily, and intuitive as possible and (b) the diagnostic categories so obtained would provide them with clinically useful information about treatment and management. A mental disorders classification that is difficult and cumbersome to implement in clinical practice and does not provide information that is of immediate value to the clinician has no hope of being implemented accurately at the encounter level in real-world health care settings. In that event, the standardisation and operationalisation of concepts and categories inherent in the classification will not guide clinical practice. Important opportunities for practice improvement and outcome assessment will be lost. A diagnostic system characterised by poor clinical utility at the encounter level cannot generate data based on those encounters that will be a valid basis for health programs and policies or global health statistics. The rationale behind these 2 studies was that how clinicians conceptualised the organisation of mental disorders as encountered in their day-to-day clinical practice was found to be (a) consistent across countries, languages, and disciplines and (b) distinct from the organisation of ICD–10; then providers could use this information to create a classification of mental disorders that corresponds more closely to clinicians’ cognitive organisation of categories and would therefore be more intuitive and efficient for real-world health care settings.

The first formative field study (17) was an internet-based study administered in both English and Spanish, in which 1,371 psychiatrists and psychologists from 64 countries participated. The second formative field study (16) involved the face-to-face administration of a standardised sorting and hierarchy-formation task to 517 mental health professionals in eight countries and five languages. Both studies found that clinicians’ conceptual map of mental disorders was rational and highly stable across profession, language, and country income levels. Moreover, both studies found that the proposed structure for mental and behavioural disorders in ICD–11 was more consistent with clinicians’ conceptual models than the structure of either ICD–10 or DSM- IV. The second study also clearly showed that clinicians preferred a ‘flatter’ structure with a larger number of groupings than a more hierarchical structure with fewer groupings, as found in ICD–10.

Harmonisation with DSM-5

The third stream of work relates to efforts to harmonise the structure of the ICD–11 chapter on Mental and Behavioural Disorders with the structure of the DSM-5, where possible. Overall, the high similarity between the overall structure of DSM-5 (1) and the proposed linear structure for ICD–11 Mental and Behavioural Disorders represents a major success of the ICD – DSM harmonisation effort. Relatively minor differences relate primarily to:

1. Proposals to combine the classifications of ‘organic’ and ‘non-organic’ aspects of conditions such as sleep disorders and sexual dysfunctions in ICD–11 in separate chapters in ways that are more consistent with current evidence and clinical practice, which were not an option for DSM-5 given that it is by definition classification of mental disorders; and
2. Differences in conventions related to residual categories and mental disorders associated with other underlying diseases under ICD–11 from decisions about the organisation of such categories in DSM-5. Additional information about the rationale for the few remaining substantive differences in overall structure between the 2 classifications is available upon request. We must emphasise that the resulting similarity in organisation between the 2 systems results from several years of complex negotiations. Given that DSM-5 has already been published, further changes to the ICD–11 structure would almost certainly move ICD–11 toward reduced similarity and harmonisation with DSM-5.

Chapter 07 – Structure of Chapter 07

Chapter 07 is a new chapter in ICD–11. It contains Sleep-wake disorders that were previously located within the respiratory, neurology, or mental health chapters. By combining these disorders into one chapter, more detail can be included for many of the sleep-related disorders. The hierarchy consists of:

1st level - Broad category of disease/disorder type

2nd level - Specific disease/disorder type

3rd level - Further specificity of disease/disorder type

Rationale for Chapter 07

As Sleep-wake disorders pertain to an area of overlap between mental health, neurological disorders and pulmonary conditions, the decision was made to place them together in one chapter.

 

Chapter 17 – Conditions related to sexual health

Structure of Chapter 17

The new chapter in ICD-11 is divided into major sections for:

• Sexual dysfunctions
• Sexual pain disorders
• Gender incongruence

1st level - Broad category of condition

2nd level - Specific type of condition

3rd level - Specific disease/disorder

The rationale for Chapter 17

The chapter has been formulated to group sexually related conditions. This also allows categorisation of gender identity-related conditions without stigmatisation, while maintaining recognition of these entities as real conditions so that it can accommodate related health interventions within the health system.

References

1. American Psychiatric Association (2013). Diagnostic and statistical manual of mental disorder, Fifth Edition (DSM-5). Washington, DC: American Psychiatric Publishing.
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3. Jablensky, A. (2009). A meta-commentary on the proposal for a meta-structure for DSM-V and ICD-11. Psychological Medicine, 39, 2099–2103.
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