The ICD‐11 is now officially in effect

The 11th revision of the International Classification of Diseases (ICD‐11) has come into effect on January 1, 2022. All the Member States of the World Health Organization (WHO) will now be asked to use this new version of the classification to report their morbidity and mortality statistics. An implementation package has been made available to facilitate the transition from the ICD‐10 to the ICD‐11.

The ICD‐11 consists of 26 chapters corresponding to groups of diseases, plus a supplementary section (Chapter V) for func­tioning assessment. Chapter 6 is on Mental, Behavioural or Neurodevelopmental Disorders. Separate chapters are provided for Sleep‐Wake Disorders (Chapter 7) and for Conditions Related to Sexual Health (Chapter 17). In addition to chapters on Injury, Poisoning or Certain Other Consequences of External Causes (Chapter 22) and on Factors Influencing Health Status or Contact with Health Services (Chapter 24), already available in the ICD‐10, a new Supplementary Chapter on Tradition­al Medicine Conditions (Chapter 26) has been added.

The main uses for which the classification is designed include: certification and reporting of causes of death; morbidity coding and reporting, including primary care; casemix and diagnosis‐related grouping (DRG); assessing and monitoring the safety, efficacy and quality of care; research and performance of clinical trials and epidemiological studies; assessing functioning; and clinical documentation (https://icd.who.int).

The ICD‐11 has 17,000 codes and more than 120,000 codable terms. It is entirely digital and accessible to everybody. It is available (by now) in English, Spanish, Chinese, Arabic and French.

The Clinical Descriptions and Diagnostic Requirements (CDDR) for mental health, corresponding to the Clinical Descriptions and Diagnostic Guidelines (CDDG) of the ICD‐10, are an integral part of the ICD‐11. They cover 20 groupings of disorders: Neurodevelopmental Disorders, Schizophrenia or Other Primary Psychotic Disorders, Catatonia, Mood Disorders, Anxiety or Fear‐Related Disorders, Obsessive‐Compulsive or Related Disorders, Disorders Specifically Associated with Stress, Dissociative Disorders, Feeding or Eating Disorders, Elimination Disorders, Disorders of Bodily Distress or Bodily Experience, Disorders Due to Substance Use or Addictive Behav­iours, Impulse Control Disorders, Disrup­tive Behaviour or Dissocial Disorders, Per­sonality Disorders and Related Traits, Para­philic Disorders, Factitious Disorders, Neu­rocognitive Disorders, Psychological or Be­havioural Factors Affecting Disorders or Dis­eases Classified Elsewhere, and Secondary Mental or Behavioural Syndromes Associated with Disorders or Diseases Classified Elsewhere.

For each category included in each of these groupings, there are sections on Es­sen­tial (Required) Features, Additional Clin­­­ical Features, Boundary with Normality (Threshold), Course Features, Developmental Pres­en­tations, Culture‐Related Features, Sex‐ and/or Gender‐Related Features, and Boundaries with Other Disorders and Conditions (Differential Diagnosis).

The development of the CDDR, to which WPA experts have extensively contributed (including through chairmanship of several Workgroups), is regarded as the most broadly international and participative pro­­cess ever implemented for a classification of mental disorders ¹ . The main differences between the CDDR and the DSM‐5 diagnostic criteria, and the main contentious issues that have been debated in the development of the CDDR, have been extensively dealt with in this journal ² , ³ , ⁴ , ⁵ , ⁶ , ⁷ , ⁸ , ⁹ , ¹⁰ , ¹¹ , ¹² , ¹³ .

The finalization of the CDDR has been preceded by a vast programme of international field studies. These included Internet‐based and clinic‐based studies. The Internet‐based field studies were implemented through the WHO Global Clinical Practice Network (https://gcp.network). This now includes more than 16,000 clinicians from 159 countries (51% psychiatrists, 30% psychologists; 40% from Europe, 25% from Western Pacific, 24% from the Americas, 5% from Southeast Asia, 3% from Eastern Mediterranean, and 3% from Africa; 63% from high‐income countries, 37% from middle‐ and low‐income countries). The clinic‐based field studies were conducted with the participation of WHO Collaborating Centres. An Internet‐based field study ¹⁴ in a sample of 928 health professionals from all WHO regions found that, on average, the ICD‐11 CDDR for ten selected mental disorders displayed significantly higher diagnostic accuracy (71.9% vs. 53.2%), as well as higher ease of use, higher clarity, better goodness of fit, and lower time required for diagnosis, compared to ICD‐10 CDDG.

An international training programme focusing on the CDDR is now being implemented. A first comprehensive online 20‐hr training course was organized by the Naples WHO Collaborating Centre on Research and Training in Mental Health and the European Psychiatric Association from 9 to 30 April, 2021. The course was coordinated by G.M. Reed and M. Maj, and covered several sections of the CDDR (Schizophrenia or Other Primary Psychotic Disorders, Mood Disorders, Anxiety or Fear‐Related Disorders, Obsessive‐Compulsive or Related Disorders, Disorders Specifically Associated with Stress, Feeding or Eating Disorders, Disorders Due to Substance Use or Addictive Behaviours, and Personality Disorders). W. Gaebel, M. Cloitre, M. Maj, C.S. Kogan, P. Monteleone, M. Swales, J.B. Saunders and N.A. Fineberg composed the Faculty. The live course was attended by 120 psychiatrists, selected from almost 500 applicants, representing 78 different countries. A further group of 250 psychiatrists had access to the course on demand.

A training course with exclusive access to the members of the WHO Global Clinical Practice Network has been set up by the WHO Collaborating Centre at Columbia University, in collaboration with the WHO Department of Mental Health and Substance Use. The course consists of 15 online training units, each focusing on a different disorder grouping and taking from 1 to 1.5 hours. Each unit provides a description of the relevant diagnostic grouping and the main innovations with respect to the ICD‐10. Knowledge check questions are provided to ensure comprehension. Participants have the opportunity to practice by applying diagnostic guidelines to clinical case examples.

A training course co‐organized by the WPA and the Global Mental Health Academy, with a structure similar to the course organized by the Naples WHO Collaborating Centre and the European Psychiatric Association, but with access also to psychologists and primary care practitioners, took place online from 8 to 29 November, 2021.

A WHO International Advisory Group on Training and Implementation for ICD‐11 Mental, Behavioural and Neurodevelopmental Disorders has been established to develop and evaluate educational, train­ing and implementation processes related to the ICD‐11 in various countries. WPA former officers who contributed to the development of the CDDR – such as M. Maj, W. Gaebel and D. Stein – are members of this Advisory Group.