The ICD‐11 has been adopted by the World Health Assembly

The 11th revision of the International Classification of Diseases and Related Health Problems (ICD‐11) has been adopted unanimously by the 72nd World Health Assembly in Geneva on May 25, 2019.

The endorsement of the new classification will not come into effect until January 1, 2022. Until that date, the Member States of the World Health Organization (WHO) will keep on using the ICD‐10 for reporting data.

In the new classification, there are chapters on conditions related to sexual health and on sleep‐wake disorders, separate from that on mental and behavioural disorders. This latter chapter includes the following groupings: neurodevelopmental disorders, schizophrenia and other primary psychotic disorders, mood disorders, anxiety and fear‐related disorders, obsessive‐compulsive and related disor‐ders, disorders specifically associated with stress, dissociative disorders, feeding and eating disorders, elimination disorders, disorders of bodily distress and bodily experience, impulse control disorders, disruptive behaviour and dissocial disorders, personality disorders, paraphilic disorders, factitious disorders, neurocognitive disorders, and mental and behavioural disorders syndromes due to disorders or diseases not classified under mental and behavioural disorders.

The finalization of the ICD‐11 chapter on mental and behavioural disorders has been preceded by a vast programme of international field studies. These included Internet‐based field studies, implemented through the Global Clinical Practice Network, including nearly 15,000 clinicians from 155 countries, which used the case vignette methodologies to examine clinical decision‐making in relationship to the proposed diagnostic categories and guidelines1, 2, and clinic‐based (or ecological implementation) field studies, assessing the reliability and clinical utility of the diagnostic guidelines with real patients3, 4.

The Internet‐based field studies reported that the diagnostic agreement for several groups of disorders (e.g., disorders specifically associated with stress, and feeding and eating disorders) was consistently higher for the ICD‐11 compared with the corresponding ICD‐10 categories (see https://gcp.network).

The ecological implementation field studies found that the interrater reliability for the main groups of mental disorders ranged from moderate to almost perfect (.45 to .88) and was generally superior to that obtained for ICD‐103. Concerning clinical utility, the diagnostic guidelines were perceived as easy to use, corresponding accurately to patients' presentations, clear and understandable, providing an appropriate level of detail, taking about the same or less time than clinicians' usual practice, and providing useful guidance about distinguishing disorder from normality and from other disorders4, 5.

Several WPA officers and experts have served as chairpersons or members of ICD‐11 Working Groups and have been involved in ICD‐11 field studies. Before that, WPA Member Societies participated in the WPA/WHO Global Survey of Psychiatrists' Attitudes Towards Mental Disorders Classification, whose results have strongly influenced the process of development of the ICD‐11 chapter on mental and behavioural disorders.

World Psychiatry has been one of the main channels through which the international mental health community has been informed about the development of the ICD‐11. In particular, the debate has focused on some crucial differences between the ICD‐11 and the DSM‐5, such as the inclusion in the former of the new categories of complex post‐traumatic stress disorder and prolonged grief disorder, and of a subtype “with chronic irritability‐anger” of oppositional defiant disorder in the place of the DSM‐5 category of disruptive mood dysregulation disorder; the absence in the former of a category for attenuated psychosis syndrome, present instead in the DSM‐5 section III; and the introduction in the former of a different approach to personality disorders, bodily distress disorders, disorders due to addictive behaviours, and disorders related to sexuality and gender identity6, 7, 8, 9, 10, 11, 12. The worldwide interactive process which has led to the ICD‐11 approach to the classification of neurocognitive disorders has also been discussed13, as well as the usefulness of a dimensional approach, recently advocated by several experts14, 15, and partially implemented in the ICD‐11.