Classification systems are essential tools in routine clinical work for providing reliable and clinically useful diagnoses, supporting clinicians and health care workers in identifying patients with higher health needs, and guiding the implementation of the best available care according to the diagnosis [Reference Reed, Roberts, Keeley, Hooppell, Matsumoto and Sharan1][Reference Keeley, Reed, Roberts, Evans and Medina-Mora2]. In psychiatric practice, classification systems are useful to improve communication among mental health professionals and researchers and to establish widely agreed descriptions of mental disorders, and should not be considered textbooks of psychopathology. Moreover, classification systems offer a framework for education on the most common clinical features of mental disorders through the organization of disorders into discrete diagnostic categories [Reference Stein, Lund and Nesse3][Reference Stein and Reed4]. A clear and straightforward classification system can help clinicians to communicate diagnosis to patients and their family members, and to reduce stigma attached to mental disorders. Finally, diagnostic systems facilitate the identification and management of mental disorders in clinical settings and have a significant predictive power [Reference First5]. It is understood, however, that they should be complemented by a more detailed clinical characterization of each individual patient [Reference Maj, Stein, Parker, Zimmerman, Fava and De Hert6] [Reference van Os, Guloksuz, Vijn, Hafkenscheid and Delespaul7].

The two most widely used classification systems in mental health are the Diagnostic and Statistical Manual of Mental Disorders (DSM), issued by the American Psychiatric Association (APA), and the International Classification of Diseases (ICD), produced by the World Health Organization (WHO). The latest version of the DSM was published in 2013, whereas the 11th revision of the ICD by the WHO has been completed in 2018 and approved by the WHO General Assembly in 2019 [Reference Pocai8]. The official reporting of health statistics by Member States to the WHO using the ICD-11 will begin on January 1, 2022 [Reference Reed, First, Kogan, Hyman, Gureje and Gaebel9].

The development of the ICD-11 chapter on mental, behavioral, and neurodevelopmental disorders represents the first major revision of the world’s foremost classification of mental disorders, which took nearly 30 years to be completed. In fact, the revision of the ICD-11 represents the biggest global, multidisciplinary, and participative process of revision of a classification system for mental disorders which has ever been implemented [Reference Reed, First, Kogan, Hyman, Gureje and Gaebel9]. Its development has involved the collaboration among several stakeholders, including some of the most eminent scientists in the field, international scientific associations, and organizations of users and carers [Reference Fuss, Lemay, Stein, Briken, Jakob and Reed10] [Reference Priebe and Miglietta11]. Furthermore, the WHO Global Clinical Practice Network, an international network including more than 16,000 clinicians from 159 countries, has been involved in the field trials of the diagnostic system [Reference Reed, First, Kogan, Hyman, Gureje and Gaebel9][Reference Reed, Rebello, Pike, Medina-Mora, Gureje and Zhao12]. The ICD-11 is currently being translated in several languages in order to be used in routine clinical practice in different parts of the world [13].

Compared with the previous versions, the ICD-11 presents several innovative features, such as the lifespan approach to mental disorders, the inclusion of a dimensional component within a system which remains mainly categorically based, and the inclusion of culture-related information [Reference Gureje, Lewis-Fernandez, Hall and Reed14][Reference Gureje, Lewis-Fernandez, Hall and Reed15][Reference Gaebel and Reed16][Reference McElroy, Shevlin, Murphy, Roberts, Makhashvili and Javakhishvili17][Reference Bryant18][Reference McCabe and Widiger19][Reference Bach, Kerber, Aluja, Bastiaens, Keeley and Claes20][Reference Zandersen and Parnas21]. The ICD-11 Clinical Descriptions and Diagnostic Guidelines (CDDG) have introduced substantial changes in order to improve the clinical utility and global applicability of diagnoses of mental disorders in routine clinical care. In particular, the guidelines provide the essential features of each disorder, including symptoms or characteristics that a clinician could reasonably expect to find in all patients affected by the same disorder [Reference Reed, First, Kogan, Hyman, Gureje and Gaebel9]. Furthermore, no cutoffs and precise diagnostic requirements are listed, unless these are empirically established across countries and cultures, in order to provide a diagnostic tool which is as close as possible to real-world clinical practice. A flexible approach has been endorsed, so that the manual can be adapted by clinicians to their clinical routine care [Reference Reed, First, Kogan, Hyman, Gureje and Gaebel9][Reference Stein, Szatmari, Gaebel, Berk, Vieta and Maj22]. The feasibility of CDDG has been confirmed by the ICD-11 field trials, which were well received by clinicians and documented a high inter-rater reliability and accuracy of diagnostic categories[23][Reference Rebello, Keeley, Kogan, Sharan, Matsumoto and Kuligyna24][Reference Luciano, Sampogna, Del Vecchio, Giallonardo, Palummo and Pocai25].

In order to adapt the classification system to the local countries’ laws, policies, health systems, and infrastructures, several multilevel actions have been subsequently implemented. Moreover, since education of health care professionals represents one of the most essential steps for the implementation and the dissemination of the new classification system in routine care, the WHO International Advisory Group led by G. M. Reed has organized training courses for professionals on the use of the ICD-11 chapter on mental, behavioral, and neurodevelopmental disorders and the relevant CDDG. Educational activities have been provided through virtual interactive formats, including an online course organized in collaboration with the European Psychiatric Association (EPA) from April 9 to 30, 2021, with the participation of several clinicians from European and non-European countries. This course was attended by 120 psychiatrists, selected from almost 500 applicants, representing 78 different countries from all over the world (e.g., from Austria, Italy, and Germany to the United States, Japan, and Thailand). During the online course, the key principles of the WHO’s ICD-11 and CDDG have been presented and discussed, with the involvement of world leaders in the field who participated in the development of CDDG and the active participation of trainees through the application of the new guidelines to clinical cases and discussion of diagnostic dilemmas. Previous training initiatives had been conducted during the 18th and 19th World Congresses of Psychiatry [Reference Ng26][Reference Schulze27][Reference Giallonardo28][Reference Perris29].

The adoption of this new classification system will represent a major change in psychiatric clinical practice worldwide. There is the need to promote educational activities in order to improve the dissemination of this innovative classification approach and to contribute to the continuous education of mental health care professionals. The EPA is committed to do so through its official channels, such as Scientific Sections, National Psychiatric Associations, and the Committees on Education and on Publications.