Classification of mental disorders

The classification schemes in common usage are based on separate (but may be overlapping) categories of disorder schemes sometimes termed "neo-Kraepelinian" (after the psychiatrist Kraepelin)[25] which is intended to be atheoretical with regard to etiology (causation). These classification schemes have achieved some widespread acceptance in psychiatry and other fields, and have generally been found to have improved inter-rater reliability, although routine clinical usage is less clear. Questions of validity and utility have been raised, both scientifically[26] and in terms of social, economic and political factors—notably over the inclusion of certain controversial categories, the influence of the pharmaceutical industry,[27] or the stigmatizing effect of being categorized or labelled.

Some approaches to classification do not use categories with single cut-offs separating the ill from the healthy or the abnormal from the normal (a practice sometimes termed "threshold psychiatry" or "dichotomous classification"[28]).[29]

Classification may instead be based on broader underlying "spectra", where each spectrum links together a range of related categorical diagnoses and nonthreshold symptom patterns.[30]

Some approaches go further and propose continuously varying dimensions that are not grouped into spectra or categories; each individual simply has a profile of scores across different dimensions.[31] DSM-5 planning committees are currently seeking to establish a research basis for a hybrid dimensional classification of personality disorders.[32] However, the problem with entirely dimensional classifications is they are said to be of limited practical value in clinical practice where yes/no decisions often need to be made, for example whether a person requires treatment, and moreover the rest of medicine is firmly committed to categories, which are assumed to reflect discrete disease entities.[33] While the Psychodynamic Diagnostic Manual has an emphasis on dimensionality and the context of mental problems, it has been structured largely as an adjunct to the categories of the DSM. Moreover, dimensionality approach was criticized for its reliance on independent dimensions whereas all systems of behavioral regulations show strong inter-dependence, feedback and contingent relationships [34][35]

Descriptive classifications are based almost exclusively on either descriptions of behavior as reported by various observers, such as parents, teachers, and medical personnel; or symptoms as reported by individuals themselves. As such, they are quite subjective, not amenable to verification by third parties, and not readily transferable across chronologic and/or cultural barriers.

Somatic nosology, on the other hand, is based almost exclusively on the objective histologic and chemical abnormalities which are characteristic of various diseases and can be identified by appropriately trained pathologists. While not all pathologists will agree in all cases, the degree of uniformity allowed is orders of magnitude greater than that enabled by the constantly changing classification embraced by the DSM system. Some models, like Functional Ensemble of Temperament suggest to unify nosology of somatic, biologically based individual differences in healthy people (temperament) and their deviations in a form of mental disorders in one taxonomy.[35][36]

In Ancient Greece, Hippocrates and his followers are generally credited with the first classification system for mental illnesses, including mania, melancholia, paranoia, phobias and Scythian disease (transvestism). They held that they were due to different kinds of imbalance in four humors.

The Persian physicians 'Ali ibn al-'Abbas al-Majusi and Najib ad-Din Samarqandi elaborated upon Hippocrates' system of classification.[38] Avicenna (980−1037 CE) in the Canon of Medicine listed a number of mental disorders, including "passive male homosexuality".

Laws generally distinguished between "idiots" and "lunatics".

Thomas Sydenham (1624–1689), the "English Hippocrates", emphasized careful clinical observation and diagnosis and developed the concept of a syndrome, a group of associated symptoms having a common course, which would later influence psychiatric classification.

Evolution in the scientific concepts of psychopathology (literally referring to diseases of the mind) took hold in the late 18th and 19th centuries following the Renaissance and Enlightenment. Individual behaviors that had long been recognized came to be grouped into syndromes.

Boissier de Sauvages developed an extremely extensive psychiatric classification in the mid-18th century, influenced by the medical nosology of Thomas Sydenham and the biological taxonomy of Carl Linnaeus. It was only part of his classification of 2400 medical diseases. These were divided into 10 "classes", one of which comprised the bulk of the mental diseases, divided into four "orders" and 23 "genera". One genus, melancholia, was subdivided into 14 "species".

William Cullen advanced an influential medical nosology which included four classes of neuroses: coma, adynamias, spasms, and vesanias. The vesanias included amentia, melancholia, mania, and oneirodynia.

Towards the end of the 18th century and into the 19th, Pinel, influenced by Cullen's scheme, developed his own, again employing the terminology of genera and species. His simplified revision of this reduced all mental illnesses to four basic types. He argued that mental disorders are not separate entities but stem from a single disease that he called "mental alienation".

Attempts were made to merge the ancient concept of delirium with that of insanity, the latter sometimes described as delirium without fever.

On the other hand, Pinel had started a trend for diagnosing forms of insanity 'without delirium' (meaning hallucinations or delusions) – a concept of partial insanity. Attempts were made to distinguish this from total insanity by criteria such as intensity, content or generalization of delusions.[39]

Pinel's successor, Esquirol, extended Pinel's categories to five. Both made a clear distinction between insanity (including mania and dementia) as opposed to mental retardation (including idiocy and imbecility). Esquirol developed a concept of monomania—a periodic delusional fixation or undesirable disposition on one theme—that became a broad and common diagnosis and a part of popular culture for much of the 19th century.[40] The diagnosis of "moral insanity" coined by James Prichard also became popular; those with the condition did not seem delusional or intellectually impaired but seemed to have disordered emotions or behavior.

The botanical taxonomic approach was abandoned in the 19th century, in favor of an anatomical-clinical approach that became increasingly descriptive. There was a focus on identifying the particular psychological faculty involved in particular forms of insanity, including through phrenology, although some argued for a more central "unitary" cause.[39] French and German psychiatric nosology was in the ascendency. The term "psychiatry" ("Psychiatrie") was coined by German physician Johann Christian Reil in 1808, from the Greek "ψυχή" (psychē: "soul or mind") and "ιατρός" (iatros: "healer or doctor"). The term "alienation" took on a psychiatric meaning in France, later adopted into medical English. The terms psychosis and neurosis came into use, the former viewed psychologically and the latter neurologically.[39]

In the second half of the century, Karl Kahlbaum and Ewald Hecker developed a descriptive categorizion of syndromes, employing terms such as dysthymia, cyclothymia, catatonia, paranoia and hebephrenia. Wilhelm Griesinger (1817–1869) advanced a unitary scheme based on a concept of brain pathology. French psychiatrists Jules Baillarger described "folie à double forme" and Jean-Pierre Falret described "la folie circulaire"—alternating mania and depression.

The concept of adolescent insanity or developmental insanity was advanced by Scottish Asylum Superintendent and Lecturer in Mental Diseases Thomas Clouston in 1873, describing a psychotic condition which generally impacts those aged 18–24 years, particularly males, and in 30% of cases proceeded to "a secondary dementia".[41]

The concept of hysteria (wandering womb) had long been used, perhaps since ancient Egyptian times, and was later adopted by Freud. Descriptions of a specific syndrome now known as somatization disorder were first developed by the French physician, Paul Briquet in 1859.

An American physician, Beard, described "neurasthenia" in 1869. German neurologist Westphal, coined the term "obsessional neurosis" now termed obsessive-compulsive disorder, and agoraphobia. Alienists created a whole new series of diagnoses that highlighted single, impulsive behavior, such as kleptomania, dipsomania, pyromania, and nymphomania. The diagnosis of drapetomania was also developed in the Southern United States to explain the perceived irrationality of black slaves trying to escape what was thought to be a suitable role.

The scientific study of homosexuality began in the 19th century, informally viewed either as natural or as a disorder. Kraepelin included it as a disorder in his Compendium der Psychiatrie that he published in successive editions from 1883.[42]

"Psychiatrists of Europe! Protect your sanctified diagnoses!" Cartoon by Emil Kraepelin, 1896.

In the late 19th century, Koch referred to "psychopathic inferiority" as a new term for moral insanity. In the 20th century the term became known as "psychopathy" or "sociopathy", related specifically to antisocial behavior. Related studies led to the DSM-III category of antisocial personality disorder.

Influenced by the approach of Kahlbaum and others, and developing his concepts in publications spanning the turn of the century, German psychiatrist Emil Kraepelin advanced a new system. He grouped together a number of existing diagnoses that appeared to all have a deteriorating course over time—such as catatonia, hebephrenia and dementia paranoides—under another existing term "dementia praecox" (meaning "early senility", later renamed schizophrenia). Another set of diagnoses that appeared to have a periodic course and better outcome were grouped together under the category of manic-depressive insanity (mood disorder). He also proposed a third category of psychosis, called paranoia, involving delusions but not the more general deficits and poor course attributed to dementia praecox. In all he proposed 15 categories, also including psychogenic neurosis, psychopathic personality, and syndromes of defective mental development (mental retardation). He eventually included homosexuality in the category of "mental conditions of constitutional origin".

The neuroses were later split into anxiety disorders and other disorders.

Freud wrote extensively on hysteria and also coined the term, "anxiety neurosis", which appeared in DSM-I and DSM-II. Checklist criteria for this led to studies that were to define panic disorder for DSM-III.

Early 20th century schemes in Europe and the United States reflected a brain disease (or degeneration) model that had emerged during the 19th century, as well as some ideas from Darwin's theory of evolution and/or Freud's psychoanalytic theories.

Psychoanalytic theory did not rest on classification of distinct disorders, but pursued analyses of unconscious conflicts and their manifestations within an individual's life. It dealt with neurosis, psychosis, and perversion. The concept of borderline personality disorder and other personality disorder diagnoses were later formalized from such psychoanalytic theories, though such ego psychology-based lines of development diverged substantially from the paths taken elsewhere within psychoanalysis.

The philosopher and psychiatrist Karl Jaspers made influential use of a "biographical method" and suggested ways to diagnose based on the form rather than content of beliefs or perceptions. In regard to classification in general he prophetically remarked that: "When we design a diagnostic schema, we can only do so if we forego something at the outset … and in the face of facts we have to draw the line where none exists... A classification therefore has only provisional value. It is a fiction which will discharge its function if it proves to be the most apt for the time".[33]

Adolph Meyer advanced a mixed biosocial scheme that emphasized the reactions and adaptations of the whole organism to life experiences.

In 1945, William C. Menninger advanced a classification scheme for the US army, called Medical 203, synthesizing ideas of the time into five major groups. This system was adopted by the Veterans Administration in the United States and strongly influenced the DSM.

The term stress, having emerged from endocrinology work in the 1930s, was popularized with an increasingly broad biopsychosocial meaning, and was increasingly linked to mental disorders. The diagnosis of post-traumatic stress disorder was later created.[43]

Mental disorders were first included in the sixth revision of the International Classification of Diseases (ICD-6) in 1949.[44] Three years later, in 1952, the American Psychiatric Association created its own classification system, DSM-I.[44]

The Feighner Criteria group described fourteen major psychiatric disorders for which careful research studies were available, including homosexuality. These developed as the Research Diagnostic Criteria, adopted and further developed by the DSM-III.

The DSM and ICD developed, partly in sync, in the context of mainstream psychiatric research and theory. Debates continued and developed about the definition of mental illness, the medical model, categorical vs dimensional approaches, and whether and how to include suffering and impairment criteria.[45] There is some attempt to construct novel schemes, for example from an attachment perspective where patterns of symptoms are construed as evidence of specific patterns of disrupted attachment, coupled with specific types of subsequent trauma.

The ICD-11 and DSM-5 are being developed at the start of the 21st century. Any radical new developments in classification are said to be more likely to be introduced by the APA than by the WHO, mainly because the former only has to persuade its own board of trustees whereas the latter has to persuade the representatives of over 200 countries at a formal revision conference. In addition, while the DSM is a bestselling publication that makes huge profits for APA, the WHO incurs major expense in determining international consensus for revisions to the ICD. Although there is an ongoing attempt to reduce trivial or accidental differences between the DSM and ICD, it is thought that the APA and the WHO are likely to continue to produce new versions of their manuals and, in some respects, to compete with one another.[33]