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 [1][2]. 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 [3][4]. 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 [5]. It is understood, however, that they should be complemented by a more detailed clinical characterization of each individual patient [6] [7].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 [8]. The official reporting of health statistics by Member States to the WHO using the ICD-11 will begin on January 1, 2022 [9].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 [9]. 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 [10] [11]. 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 [9][12]. 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 s...