The classification of mental disorders, also known as psychiatric nosology or psychiatric taxonomy, is central to the practice of psychiatry and other mental health professions.
The two most widely used psychiatric classification systems are the International Classification of Diseases, 11th edition (ICD-11; in effect since 1 January 2022.), produced by the World Health Organization (WHO); and the Diagnostic and Statistical Manual of Mental Disorders produced by the American Psychiatric Association since 1952. The latest edition is the Fifth Edition, Text Revision (DSM-5-TR), which was released in 2022. The ICD is a broad medical classification system; mental disorders are contained in Chapter 06: Mental, behavioural or neurodevelopmental disorders ().
Both systems list disorders thought to be distinct types, and in recent revisions the two systems have deliberately converged their codes so that their manuals are often broadly comparable, though differences remain. Both classifications employ operational definitions.
Other classification schemes, used more locally, include the Chinese Classification of Mental Disorders.
Manuals of limited use, by practitioners with alternative theoretical persuasions, include the Psychodynamic Diagnostic Manual.
Definitions In the scientific and academic literature on the definition or categorization of mental disorders, one extreme argues that it is entirely a matter of value judgments (including of what is normal) while another proposes that it is or could be entirely objective and scientific (including by reference to statistical norms); other views argue that the concept refers to a "fuzzy prototype" that can never be precisely defined, or that the definition will always involve a mixture of scientific facts (e.g. that a natural or evolved function is not working properly) and value judgments (e.g. that it is harmful or undesired).Perring, C. (2005) Mental Illness Stanford Encyclopedia of Philosophy Lay concepts of mental disorder vary considerably across different cultures and countries, and may refer to different sorts of individual and social problems.
The WHO and national surveys report that there is no single consensus on the definition of mental disorder, and that the phrasing used depends on the social, cultural, economic and legal context in different contexts and in different societies. The WHO reports that there is intense debate about which conditions should be included under the concept of mental disorder; a broad definition can cover mental illness, intellectual disability, personality disorder and substance dependence, but inclusion varies by country and is reported to be a complex and debated issue. There may be a criterion that a condition should not be expected to occur as part of a person's usual culture or religion. However, despite the term "mental", there is not necessarily a clear distinction drawn between mental (dys)functioning and brain (dys)functioning, or indeed between the brain and the rest of the body. PDF
Most international clinical documents avoid the term "mental illness", preferring the term "mental disorder". However, some use "mental illness" as the main overarching term to encompass mental disorders.Office of the Surgeon General and various United States Government agencies (1999) Mental Health: A report of the Surgeon General Some consumer/survivor movement organizations oppose use of the term "mental illness" on the grounds that it supports the dominance of a medical model. The term "serious mental impairment" (SMI) is sometimes used to refer to more severe and long-lasting disorders while "mental health problems" may be used as a broader term, or to refer only to milder or more transient issues.US Department of Health and Human Sciences (2007) Mental Health & Mental Disorders: Terminology Confusion often surrounds the ways and contexts in which these terms are used.Economic and Social Research Council Mental Health and Mental Illness in the UK
Mental disorders are generally classified separately to neurological disorders, learning disabilities or intellectual disabilities.
Classification systems
ICD-10
The International Classification of Diseases (ICD) is an international standard diagnostic classification for a wide variety of health conditions. The ICD-10 states that mental disorder is "not an exact term", although it is generally used "...to imply the existence of a clinically recognisable set of symptoms or behaviours associated in most cases with distress and with interference with personal functions." Chapter V focuses on "mental and behavioural disorders" and consists of 10 main groups:The ICD-10 Classification of Mental and Behavioural Disorders (WHO, 1992): Clinical descriptions and diagnostic guidelines). " "Disorder" is not an exact term, but it is used here to imply the existence of a clinically recognizable set of symptoms or behaviour associated in most cases with distress and with interference with personal functions. Social deviance or conflict alone, without personal dysfunction, should not be included in mental disorder as defined here." (p.11)
F0 – F9: Organic, including symptomatic mental disorders F10 – F-19: Mental and behavioural disorders due to use of psychoactive substances F20 – F29: Schizophrenia, schizotypal and delusional disorders F30 – F39: Mood (affective) disorders F40 – F49: Neurotic, stress-related and somatoform disorders F50 – F59: Behavioural syndromes associated with physiological disturbances and physical factors F60 – F69: Disorders of personality and behaviour in adult persons F70 – F79: Mental retardation F80 – F89: Disorders of psychological development F90 – 98: Behavioural and emotional disorders with onset usually occurring in childhood and adolescence In addition, a group of F99 "unspecified mental disorders".
Within each group, there are more specific subcategories.
ICD-11
The WHO has revised ICD-10 to produce the latest version, ICD-11, adopted by the 72nd World Health Assembly in 2019, and came into effect on 1 January 2022. The ICD is a broad medical classification system; mental disorders are contained in Chapter 06: Mental, behavioural or neurodevelopmental disorders ().
DSM-IV
The DSM-IV was originally published in 1994 and listed more than 250 mental disorders. It was produced by the American Psychiatric Association and it characterizes mental disorder as "a clinically significant behavioral or psychological syndrome or pattern that occurs in an individual,...is associated with present distress...or disability...or with a significantly increased risk of suffering" but that "...no definition adequately specifies precise boundaries for the concept of 'mental disorder'...different situations call for different definitions" (APA, 1994 and 2000). The DSM also states that "there is no assumption that each category of mental disorder is a completely discrete entity with absolute boundaries dividing it from other mental disorders or no mental disorders."
The DSM-IV-TR (Text Revision, 2000) consisted of five axes (domains) on which disorders could be assessed. The five axes were: Axis I: Clinical Disorders (all mental disorders except Personality Disorders and Mental Retardation) Axis II: Personality Disorders and Mental Retardation Axis III: General Medical Conditions (must be connected to a Mental Disorder) Axis IV: Psychosocial and Environmental Problems (for example, limited social support network) Axis V: Global Assessment of Functioning (Psychological, social and job-related functions are evaluated on a continuum between mental health and extreme mental disorder)
The axis classification system was removed in the DSM-5 and is now mostly of historical significance. The main categories of disorder in the DSM are: DSM Group Examples Disorders usually first diagnosed in infancy, childhood or adolescence. *Disorders such as ADHD and epilepsy have also been referred to as developmental disorders and developmental disabilities. ADHD Delirium, dementia, and amnesia and other cognitive disorders Alzheimer's disease Mental disorders due to a general medical condition AIDS-related psychosis Substance-related disorders Alcohol use disorder Schizophrenia and other psychotic disorders Delusional disorder Mood disorders Major depressive disorder, Bipolar disorder Anxiety disorders Generalized anxiety disorder, Social anxiety disorder Somatoform disorders Somatization disorder Factitious disorders Münchausen syndrome Dissociative disorders Dissociative identity disorder Sexual and gender dysphoria Dyspareunia, Gender dysphoria Eating disorders Anorexia nervosa, Bulimia nervosa Sleep disorders Insomnia Impulse control disorders not elsewhere classified Kleptomania Adjustment disorders Adjustment disorder Personality disorders Narcissistic personality disorder Other conditions that may be a focus of clinical attention Tardive dyskinesia, Child abuse
DSM-5
The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) is the 2013 update to the Diagnostic and Statistical Manual of Mental Disorders, the taxonomic and diagnostic tool published by the American Psychiatric Association (APA). In 2022, a revised version (DSM-5-TR) was published. In the United States, the DSM serves as the principal authority for psychiatric diagnoses.
The DSM-5 is not a major revision of the DSM-IV-TR, but the two have significant differences. Changes in the DSM-5 include the re-conceptualization of Asperger syndrome from a distinct disorder into autism spectrum disorder; the elimination of subtypes of schizophrenia; the deletion of the "bereavement exclusion" for depressive disorders; the renaming and reconceptualization of gender identity disorder to gender dysphoria; the inclusion of binge eating disorder as a discrete eating disorder; the renaming and reconceptualization of paraphilias, now called paraphilic disorders; the removal of the five-axis system; and the splitting of disorders not otherwise specified into other specified disorders and unspecified disorders.
Other schemes The Chinese Society of Psychiatry's Chinese Classification of Mental Disorders (currently CCMD-3) The Latin American Guide for Psychiatric Diagnosis (GLDP). The Research Domain Criteria (RDoC), a framework being developed by the National Institute of Mental Health The Hierarchical Taxonomy of Psychopathology (HiTOP), developed by the HiTOP consortium, a group of psychologists and psychiatrists who had a record of scientific contributions to classification of psychopathology.
Childhood diagnosis Child and adolescent psychiatry sometimes uses specific manuals in addition to the DSM and ICD. The Diagnostic Classification of Mental Health and Developmental Disorders of Infancy and Early Childhood (DC:0-3) was first published in 1994 by Zero to Three to classify mental health and developmental disorders in the first four years of life. It has been published in 9 languages.Zero to Three. (1994). Diagnostic classification: 0–3: Diagnostic classification of mental health and developmental disorders in infancy and early childhood. Washington, DC. The Research Diagnostic criteria-Preschool Age (RDC-PA) was developed between 2000 and 2002 by a task force of independent investigators with the goal of developing clearly specified diagnostic criteria to facilitate research on psychopathology in this age group. The French Classification of Child and Adolescent Mental Disorders (CFTMEA), operational since 1983, is the classification of reference for French child psychiatrists.
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