Neurocognitive disorders in ICD‐11: the debate and its outcome

In the ICD‐11, the chapters “06. Mental, behavioural or neurodevelopmental disorders” and “08. Diseases of the nervous system” are going to include, respectively, the groupings of “Neurocognitive disorders” and “Disorders with neurocognitive impairment as a major feature”. Concern over the “wrong” allocation of dementias in the diagnostic system had produced many critical reactions from mental health professionals, due to the anticipated adverse consequences for treatment and care. Here we summarize the background and outcome of these reactions.

In late 2016, the World Health Organization (WHO) moved the dementia categories – contrary to the “traditional” location of clinical manifestations in ICD‐10 (F00‐F03) – from chapter 06 to chapter 08 of the ICD‐11 draft. This step, following a Neurology Topic Advisory Group proposal, generated written protest notes by about two dozens of national and international scientific associations, mainly from psychiatry, old age psychiatry, psychology and other mental health workforce. In early 2017, the WHO corrected the previous step in that the dementia categories were moved back to chapter 06.

What was the rationale of these moves? According to the ICD‐11 Reference Guide, the guiding principles for “allocation of entities” are “to maintain the structural and functional integrity” of the classification and “to preserve consistency with previous versions”. Classification should be changed only with a “strong rationale”, and categories should be kept in their “legacy location” if they “could arguably be in two or more places”.

Neurocognitive disorders such as Alzheimer dementia are being classified in ICD‐10 according to the dagger‐asterisk system, with the clinical manifestation in chapter F (F00*) and the aetiology in chapter G (G30†). In ICD‐11, according to this “legacy location”, Alzheimer dementia should continue to be classified both in chapter 06 (“disorders”) for its manifestation and in chapter 08 (“diseases”) for its aetiology, using the new post‐coordination coding.

Despite increasing knowledge on aetiopathogenesis and biomarkers, dementias are generally still diagnosed clinically and classified according to their manifestation. The proposal to move them to chapter 08 may have been either misled by concept or misread by the WHO, although the ultimate aim of classifying disease entities is indeed to primarily build on aetiologies and dysfunctional body systems and not solely on clinical manifestations. Despite Griesinger's dictum “mental disease is brain disease”1, and although involvement of brain dysfunction is increasingly recognized and important to consider, most “mental” disorders cannot be treated as “brain disorders” or diseases with monocausal brain pathology.

Arguments against the move of dementias to chapter 08 were referring to WHO managing issues (move contrary to the joint recommendation by Mental Health and Neurology Topic Advisory Groups), conceptual and methodological issues (lack of evidence for the move; the need for a biopsychosocial approach in integrated care), treatment and service issues (resulting limitation of access to care; importance of neuropsychological vs. biomedical measures in treatment and care), professional and interdisciplinary issues (cross‐national variation in responsibility of specialties, but usually major role of psychiatrists in treatment and care; importance of keeping the balance among disciplines), economic issues (problems with reimbursement by insurance companies in several countries if dementia is withdrawn from chapter on mental and behavioural disorders), psychopathological issues (behavioural symptoms do not belong in the “neurology” section, while being a major burden for patients and carers and hence a significant focus for treatment), and classification analogies in ICD‐11 (e.g., chapters on cardiovascular, infectious and endocrinological diseases).

As an outcome of the debate, the WHO has moved dementias back to mental disorders in chapter 06, analogously to ICD‐10 and DSM‐5. Chapter 08 covers in its neurocognitive section only “diseases”, e.g. Alzheimer disease, which can be associated by post‐coordination coding with “6E00 Dementia due to Alzheimer disease”. Options for post‐coordination coding have now also been implemented for “6D91 Mild neurocognitive disorder” (F06.7 in ICD‐10), which can be associated with any of the diseases in chapter 08, or with diseases classified elsewhere, as a result of commentaries by the Japanese Society of Psychiatry and Neurology (JSPN), the German Association of Psychiatry and Psychotherapy, and the American Psychiatric Association.

Another proposal by JSPN was the introduction of specifiers for behavioural symptoms in the diagnosis of dementias, because of their high burden for patients and carers. This has been implemented by the WHO under “6E20 Behavioural or psychological disturbances in dementia”.

In conclusion, we have witnessed successful outcomes from a worldwide interactive process with the WHO on classifying neurocognitive disorders taking into account clinical utility2. In keeping abreast of the ever developing state of the art, the ICD‐11 will need ongoing adaptation, e.g., taking into account the progress in preclinical classification of Alzheimer dementia and biomarker‐based diagnosis3.

Wolfgang Gaebel1,2, Frank Jessen3,4, Shigenobu Kanba5,6
1Department of Psychiatry and Psychotherapy, Medical Faculty, Heinrich‐Heine University, Düsseldorf, Germany; 2WHO Collaborating Centre on Quality Assurance and Empowerment in Mental Health, Düsseldorf, Germany; 3Department of Psychiatry, Medical Faculty, University of Cologne, Cologne, Germany; 4German Center for Neurodegenerative Diseases, Bonn, Germany; 5Department of Neuropsychiatry, Kyushu University, Fukuoka, Japan; 6Japanese Society of Psychiatry and Neurology, Tokyo, Japan

Unless specifically stated, the views expressed in this letter are those of the authors and do not represent the official policies or positions of the WHO.