# 04 - Key approaches to classifying mental, behavio # Key approaches to classifying mental, behavioural and neurodevelopmental disorders 9 Key approaches to classifying mental, behavioural and neurodevelopmental disorders The definition of mental, behavioural and neurodevelopmental disorders The ICD-11 chapter on mental, behavioural and neurodevelopmental disorders begins with the following definition: Mental, behavioural and neurodevelopmental disorders are syndromes characterized by clinically significant disturbance in an individual’s cognition, emotional regulation or behaviour that reflects a dysfunction in the psychological, biological or developmental processes that underlie mental and behavioural functioning. These disturbances are usually associated with distress or impairment in personal, family, social, educational, occupational or other important areas of functioning. The term “disorder” is used as a part of nearly all category titles in the chapter. Although “disorder” is not a precise term, as in ICD-10 its use is intended “to avoid even greater problems inherent in the use of terms such as ‘disease’” (15, p. 11), which implies greater certainty about etiology and pathophysiology than exists for most mental disorders. Although mental disorders are by definition syndromes, “syndrome” is a broader term with more variable usage. Its use in category titles in the classification of mental, behavioural and neurodevelopmental disorders is restricted to the grouping of secondary mental or behavioural syndromes associated with disorders and diseases classified elsewhere; these are conditions with more variable symptoms that are less specified in the CDDR, but are judged to be direct pathophysiological consequences of a medical condition. Other conditions referred to as syndromes that are mentioned in the CDDR are classified in other parts of ICD-11 (e.g. Tourette syndrome is included in the chapter on diseases of the nervous system). Beyond the issue of terminology, the definition of mental, behavioural and neurodevelopmental disorders helps to delineate two boundaries. The first is the boundary between mental, behavioural and neurodevelopmental disorders and diseases and disorders classified in other chapters of ICD-11, and the second is the boundary between mental, behavioural and neurodevelopmental disorders and normality. Both of these boundaries represent key issues in diagnosis. The first part of the definition (“clinically significant disturbance in an individual’s cognition, emotional regulation or behaviour”) indicates that the essential features of the disorders included in the ICD-11 chapter on mental, behavioural and neurodevelopmental disorders invariably involve (but are not limited to) symptoms from these domains of mental and behavioural functioning. The presentation of disorders in other ICD-11 chapters (e.g. those on diseases of the nervous system and sleep-wake disorders) may include disturbances in these domains, but they are not common to all the disorders in those chapters. The second part of the definition is intended to clarify that in order for a clinical presentation to be diagnosable as a mental, behavioural or neurodevelopmental disorder (as opposed to representing normal variation), the symptom must reflect a dysfunction in an underlying psychological, biological or developmental process. For example, the experiences of an individual who has recently been bereaved might include acute feelings of sadness and emptiness accompanied by disturbances in cognition, emotional regulation or behaviour. However, symptoms entirely attributable to grief are not in and of themselves indicative of an underlying dysfunction in a psychological, biological or developmental process. Normal bereavement is not considered to be a disorder, despite its potential negative impact on social and occupational functioning. Similarly, behaviour (e.g. political, religious, sexual) that deviates from the accepted standards of society is only considered to be symptomatic of a mental disorder if it is a manifestation of a dysfunction in a psychological, biological or developmental process. Introduction Clinical Descriptions and Diagnostic Requirements for ICD-11 Mental, Behavioural or Neurodevelopmental Disorders The final part of the definition (“these disturbances are usually associated with distress or impairment in personal, family, social, educational, occupational or other important areas of functioning”) notes that distress in the individual and/or impairment in functioning is commonly a consequence of the symptoms, and for many mental disorders is an essential feature. At the same time, it is not always required (e.g. individuals experiencing a hypomanic episode in the context of bipolar type II disorder often do not experience distress about their condition, and by definition do not exhibit functional impairment), hence the use of “usually” in the definition. Structure of the chapter on mental, behavioural and neurodevelopmental disorders The organization of the ICD-10 chapter on mental and behavioural disorders had been dictated in part by the ICD-10 coding system itself. The first character of ICD-10 codes, which indicated the chapter, was alphabetical, thus allowing for up to 26 chapters. The second character, which indicated the diagnostic grouping within the chapter, was numerical, effectively limiting the number of possible diagnostic groupings within a chapter to 10. The use of alphanumeric characters throughout the ICD-11 coding system removes those artificial constraints. Consequently, there are 21 diagnostic groupings in the ICD-11 chapter on mental, behavioural and neurodevelopmental disorders. A few of the ICD-11 diagnostic groupings are completely parallel to ICD-10 groupings (e.g. disorders due to substance use, schizophrenia and other primary psychotic disorders, mood disorders). Most of the other ICD-10 diagnostic groupings were split into multiple ICD-11 groupings. For example, ICD-10 neurotic, stress-related and somatoform disorders was split into five ICD-11 diagnostic groupings: anxiety and fear-related disorders; obsessive-compulsive and related disorders; disorders specifically associated with stress; dissociative disorders; and bodily distress disorders. In one case, three ICD-10 diagnostic groupings (mental retardation; disorders of psychological development; and behavioural and emotional disorders with onset usually occurring in childhood and adolescence) were combined into a single neurodevelopmental disorders grouping in ICD-11, although some of the disorders that were included in the behavioural and emotional disorders with onset usually occurring in childhood and adolescence grouping in ICD-10 were placed into other ICD-11 diagnostic groupings based on symptomatic presentations (e.g. conduct disorders were placed in the disruptive behaviours or dissocial disorders grouping in ICD-11). Disorders of intellectual development in ICD-11 have been reconceptualized from ICD-10 mental retardation such that they are assessed based on adaptive behaviour functioning in addition to intellectual functioning. The elimination of ICD-10 diagnostic groupings explicitly linked to onset of the condition during childhood and adolescence is in part related to the decision to adopt a lifespan approach to the description of diagnostic categories in ICD-11. Each category contains a section on developmental presentations, which describes the manifestations of the disorder in early and middle childhood, adolescence and older adulthood, to the extent possible based on available evidence. The ICD-11 CDDR also include descriptions of adult presentations of most disorders described exclusively in terms of children in the ICD-10 CDDG (e.g. attention deficit hyperactivity disorder, separation anxiety disorder, conduct disorder, pica). Four diagnostic subgroupings were moved out of the mental, behavioural and neurodevelopmental disorders chapter entirely and placed within other ICD-11 chapters: ICD-10 nonorganic sleep disorders were moved to the ICD-11 chapter on sleep-wake disorders, ICD-10 sexual dysfunctions not caused by organic disorder or disease and gender identity disorders were moved to the ICD-11 chapter on conditions related to sexual health, and ICD-10 tic disorders were moved to the ICD-11 chapter on diseases of the nervous system. The movement of sleep-wake disorders and sexual dysfunctions to new, separate chapters in no way indicates that these conditions are 11 not appropriately treated by mental health professionals. Rather, it reflects an effort to remove the artificial and scientifically and clinically inaccurate “mind–body split” embodied in the designation of “organic” and “nonorganic” forms of these disorders. The inclusion of ICD-11 gender incongruence in the chapter on conditions related to sexual health reflects the conclusion that these conditions are not appropriately viewed as mental disorders based on a series of international field studies indicating that distress and functional impairment in transgender people is predicted by experiences of stigmatization and victimization rather than being an intrinsic characteristic of being transgender (57–59). Categories and dimensions ICD-10 was almost entirely categorical in nature (categories were either present or absent), with the only exceptions being severity-based subcategories for mental retardation (mild, moderate, severe, profound) and depressive episode (mild, moderate, severe). ICD-11 has moved beyond a strictly categorical approach, incorporating dimensional elements in two different ways. First, in addition to intellectual developmental disorder and depressive episode, bodily distress disorder, personality disorder and dementia are subcategorized based on severity (mild, moderate, severe). Second, a number of mental disorders allow for the indication of symptomatic manifestations that are intended to provide dimensional profiles that cut across different disorders in a particular grouping. These include symptomatic manifestations of primary psychotic disorders (positive symptoms, negative symptoms, depressive mood symptoms, manic mood symptoms, psychomotor symptoms, cognitive symptoms), which can be further coded as not present, mild, moderate or severe, and prominent personality trait domains in personality disorders (negative affectivity, detachment, asociality, disinhibition, anankastia). See the following section on using the CDDR for ICD-11 mental, behavioural and neurodevelopmental disorders in clinical settings for specific examples of how these dimensional specifiers are coded. Cultural factors Because the CDDR will be employed around the world as a basis for diagnosis and treatment selection among people living in diverse social milieus and cultural contexts, a key priority in development of the diagnostic material was to consider and reflect the influence of culture. Cultural factors affect the diagnosis of mental, behavioural and neurodevelopmental disorders in complex and multifaceted ways. For example, culture can influence how disorders are conceptualized, experienced and expressed; what is considered normal or pathological; how functioning is affected; where and how people seek care; and the ways that patients and families participate in treatment. Attention to culture was also in line with the overall priority of the revision process to enhance the clinical utility and global applicability of the CDDR. Information that makes the diagnostic system more relevant and acceptable to clinicians and service users around the world can enhance the usefulness of the CDDR as tool for identifying those who require care and connecting them to services. WHO appointed a Working Group on Cultural Considerations to develop material on culture for the CDDR. This Working Group conducted extensive consultations with experts from around the world, and systematically reviewed the literature on cultural influences on diagnosis and psychopathology for each diagnostic category, as well as relevant material on culture from ICD-10 and DSM-5. Information was also collated from materials produced by other ICD-11 working groups as part of their generation of proposed content for their respective diagnostic areas. On this basis, the Working Group developed a section entitled “culture-related features” for diagnostic categories in the CDDR. The focus was on providing pragmatic, actionable material to assist clinicians in using the CDDR to evaluate patients in a culturally informed manner and reduce bias in clinical decision-making. This section is meant to be of practical use in the process Introduction