Evolution of Diagnostic Criteria in Psychoses

By Thomas A. Ban



        The term "psychosis" was introduced in the mid-19th century for the separation of psychiatric disorders from neurological disorders within the "neuroses." The concept of "psychosis" has become gradually restricted from a generic term for psychiatric disorders to one of the "major classes" of mental illness which was assumed to be the result of a disease process and most recently to a "symptom" present in many psychiatric disorders. In the course of this development diagnostic criteria of "psychosis" shifted from the severity of the clinical manifestations and the degree of the impairment in social functioning, to the presence of one or more "symptom" from a set of "psychopathological symptoms" which include hallucinations, formal thought disorder manifest in disorganized or odd speech, delusions, flat / inappropriate affect, avolition / apathy, disorganized behavior, catatonic motor behavior and depersonalization / derealization. The changes in the conceptualization of "psychosis" and in the diagnostic criteria of "psychosis" are documented in the diagnostic and statistical manuals of the American Psychiatric Association (from DSM-I to DSM- IV) and the international classifications of the World Health Organization (from ICD-9 to ICD-10).


Introduction: From Neurosis to Psychosis

        The term "neurosis" was introduced in the medical literature by William Cullen (1) in the mid-1780s (2). Cullen (1) believed that "life is a function of nervous energy, muscle a continuation of nerve, and disease mainly nervous disorder," and classified illness into "fever," cachexias," "local diseases" and "neuroses" (3), i.e., diseases which were assumed to have their "seat in the nervous system" (4).

        To shift emphasis in the conceptualization of "insanity" (1) from the "nerves" to the "soul" ("anima" or "psyche"), the term "Psychiaterie" was introduced by Johann Christian Reil (5) in 1803. It was adopted by Johann Christian Heinroth (6), and changed to "Psychiatrie," in his influential text, published in 1818. Introduction of the term "psychiatry" profoundly affected the subject matter and the development of the field; for well over 100 years psychiatric opinion remained divided as to whether "psychiatry" deals with Cullen's (1) disorders of the "nerves" (body) or Reil's (5) disorders of the "soul" (mind) (7).

        The terms "neurosis" and "psychiatry" were used interchangeably during the second quarter of the 19th century (2). Recognition, however, that not "every defect of the nervous system was accompanied by mental disorder," led to the introduction of the term "psychosis" by Ernst Feuchsterleben (8) in 1845. In his "textbook on medical psychology," Feuchsterleben (8) declared that "every psychosis is a neurosis, because, without the nerves as intermediaries, no psychological change can be exhibited, but not every neurosis is a psychosis," using the term "psychosis" for the first time in the psychiatric literature (2).

        By separating the "disorders of the nerves" with mental pathology, from the "disorders of the nerves" without mental pathology, i.e., "psychiatric disorders" from "neurological disorders," the concept of "psychosis" provided the necessary orientation points for the development of the discipline which have been referred to "psychiatry" to-date (9).


The Unitary Concept of Psychosis

        "Psychosis," during the mid-19th century, was an all embracing diagnostic concept which included all the different "general forms of insanity" separated by Esquirol (10), i.e., "lypemania" ("melancholia of the ancient"), "monomania" ("partial insanity"), "mania" ("pure insanity"), "dementia," and "imbecility" (or "idiocy") and all the different "mental states" described by Griesinger (11), i.e., "mental depressions" ("lypemania"), "mental exaltations" ("monomania" and "mania"), and "mental weakness'" ("dementia" and "imbecility").

        Griesinger (11) perceived "psychosis" ("insanity") as a symptom of brain disease, and considering Bayle's (12) findings that the "state of dementia" was preceded by a " state of monomania" and a "state of mania" in "chronic arachnitis," he suggested that the various mental states are different developmental stages of one and the same disease process (13). In his classic text on the "pathology and therapy of mental illness," Griesinger (11) adopted Guislain's (14) "unitary concept of Psychosis" ("Einheitpsychose") and postulated that in the mental syndromes in which neuropathological changes are absent, they will become detectable at a later stage of disease development (15).

        In keeping with the concept of "Einheitpsychose," is Morel's (16) "theory of degeneration," the first genetic theory of mental illness. It is based on the assumption that "psychosis" is the result of an "innate biological defect" which becomes manifest in increasingly severe mental syndromes in lineal descents. Morel's (16) "theory" was replaced towards the end of the 19th century by Moebius” (17) "endogeny theory," which implied only a "constitutionally determined predisposition" for developing "psychosis." Nevertheless, "genetic anticipation," the essential feature of Morel's (16) theory, has been lingering on to-date, and was linked during the 1990s, to "trinucleotide repeat mutations" by molecular genetic research (18, 19).


Classification of Psychoses

        By the dawn of the 20th century the concept of "neurosis," which once embraced both the "psychiatric" and the "neurological disorders, " became restricted to one of the two major classes of psychiatric disease and the concept of "psychosis," which once embraced all "psychiatric disorders," became restricted to the other major class. Instrumental to this development was Freud's (20) separation of the "neuroses" into "actual neuroses," and "psychoneuroses" and Kraepelin's (21) adoption of the terms "psychosis" ("infection psychoses," "exhaustion psychoses, “intoxication psychosis” "thyrogenous psychoses," “involution psychoses") and "neurosis" ("psychogenic neuroses") in the sixth edition of his "textbook of psychiatry." Furthermore, by introducing his diagnostic concepts of "manic depressive insanity" in the same edition, he set the foundation and "dementia praecox" of the "Kraepelinian dichotomy" of "endogenous psychoses" (22) and opened the path for the dividing of "psychoses" into "organic" and "functional."

        An important further development in the classification of "psychoses" was Bonhoeffer's (23) separation of the "exogenous," or "symptomatic psychoses" --associated with "toxic agents," "infections," or "systemic disease" -- from the "organic psychoses," associated with "course brain disease," dividing the "somatically determined psychoses" into "organic" and "symptomatic." Another important further development was Wimmer's (24) separation of the "psychogenic psychoses," triggered by "psychic trauma," or "stressful life events," from the "endogenous psychoses," dividing the "functional psychoses" into "reactive" and "endogenous."


Concepts of Psychoses

Psychosis as Disease Process

        In spite of its frequent use, the term, "psychosis" remained vaguely defined (9) until Jaspers' (25) separation of "disease process" from "personality development" in 1910. Three years later, in his classic text on "general psychopathology," Jaspers (26, 27) defines "psychosis" as disease, which "seizes upon the individual as a whole, regardless whether it is a hereditary disorder beginning at a certain time of life, or a non-hereditary disorder which is called into being by an exogenous lesion." To qualify for Jaspers' (26) criteria of "psychosis," the "pathological process," displayed in patient's "case history," has to be sufficiently strong to override "normal development," displayed in patient's "life history"; and patient's "behavior" has to be sufficiently different that it "can not be understood as an extension of the normal," or as "an exaggerated response to ordinary experience."

        Jaspers’ (26) conceptual framework was adopted by Kurt Schneider (28) in his rudimentary classification in which the "psychoses," i.e., "effects of illness," were separated from the "abnormal variations of psychic life," i.e., "anomalies of development," which might become manifest in "abnormal intellectual endowment, "abnormal personality" or "abnormal psychic reactions." Schneider (28) defines the "psychoses" as diseases with "psychic symptomatology" and "somatic etiology," and divides the "psychoses" into "somatically determined psychoses, " " cyclothymia," the term he used for Kraepelin's (21) "manic depressive insanity" and "schizophrenia" (29), a term he retained in spite of his belief that "there is nothing to which one could point as a common element in all the clinical pictures" subsumed under this diagnostic category.


Socio-Medical Concept of Psychosis

        Jaspers’ (26) "disease concept" of "psychosis" was transformed into a "socio-medical concept" by Fish (30) with consideration that the characteristic features of "psychosis" include "psychopathological manifestations," such as "lack of insight," "distortion of the whole personality by the illness," "construction of false environment out of subjective experiences," and "gross disorder of basic drives," including "self- preservation," coupled with an "inability to make a reasonable social adjustment."

        The interaction between "psychopathology" and "social adjustment" is further elaborated in the Diagnostic Criteria for Research (DCR) Budapest-Nashville (31) in which "psychosis" is defined as a "nonspecific syndrome," characterized by "lack of insight," and "psychopathological symptoms" of sufficient severity to "disrupt everyday functioning" with "collapse of customary way of social life" which may call for psychiatric hospitalization. In the DCR, "psychosis" is the "nadir" in the process of "psychiatric illness," the point at which patient's "case history" ("pathological process"), displayed in "psychopathological symptoms," such as "hallucinations," "autism," become dominant over patient's "life history" ("normal development"). During "psychosis" there is a forced withdrawal from everyday life, accompanied by a tendency to suspend social adjustment; and during the period of hospitalization, social adjustment may collapse to the extent that it may not be possible to assess social adjustment at all. Without encountering such a "nadir" at least one time in the course of the illness, the prerequisite for a DCR diagnosis of "psychosis" is not fulfilled.

        "Psychoses" in the DCR are divided into "somatically determined" and "functional;" "functional psychoses" into "reactive" (24, 28) and "endogenous" (32) with the "delusional psychoses" (33, 34, 35, 36) in between; "endogenous psychoses," into "affective" (including "manic depressive illness," "pure melancholia, " "pure mania," "pure depressions," and "pure euphorias"), "cycloid," and "schizophrenic;" and "schizophrenic psychoses" into "unsystematic" ("cataphasia," "affect-laden paraphrenia" and "periodic catatonia") and "systematic" ("paraphrenias," i.e., "phonemic," "hypochondriacal," "confabulatory," "grandiose," "fantastic," and "incoherent;" "hebephrenias," i.e., "autistic," "eccentric," "shallow" and "silly;" and "catatonias," i.e., "parakinetic," "proskinetic," "speech prompt," "speech inactive," "manneristic" and "negativistic" (32).


Psychosis in Consensus-Based Classifications

        To overcome the difficulties created by the different diagnostic criteria used for the same diagnostic terms by different schools of psychiatry and in different cultures and language areas, consensus based classifications were developed by the World Health Organization (37, 38, 39) and the American Psychiatric Association (40, 41, 42, 43, 44). A consensus based classification is a set of diagnostic formulations agreed upon by a body of experienced and well informed psychiatrists (45).



        The first consensus based classification with a description of its diagnostic terms was the first edition of the American Psychiatric Association's (40) Diagnostic and Statistical Manual of Mental Disorders (DSM-I) published in 1952. It was based on Adolf Meyer's (46) "psychobiological view" that "mental disorders" represent "reactions of the personality" to "social," "psychological" and "biological" factors, and that "psychoses" are "whole reactions," in variance with the "other psychiatric disorders" which are only "part reactions" (47, 48).

        Mental disorders in the DSM-I are divided into two (or three with the inclusion of "mental deficiency") classes of illness, i.e., (a) "organic disorders," caused by or associated with impairment of brain tissue function, and (b) "disorders of psychogenic origin or without clearly defined physical cause or structural changes in the brain." "Psychotic disorders," including "involutional, ""affective" ("manic depressive reactions," and "psychotic depressive reactions"), "schizophrenic," and "paranoid reactions, " are one of the five categories of the second class.

        "Psychotic disorders" in the DSM-I (40) are defined as diseases characterized by "personality disintegration," "failure to test and evaluate correctly external reality," and "inability to relate effectively to people or work." In "affective reactions," the "psychosis" is characterized by "severe mood disturbance," with the mood alterations of thought and behavior "in consonance with the affect." In "schizophrenic reactions," by fundamental disturbances in reality relationships and concept formation with associated affective, behavioral, and intellectual disturbances marked by a tendency to retreat from reality, regressive trends, bizarre behavior, disturbances in the stream of thought, and delusions."

        In addition, the qualifying phrase, "with psychotic reaction," is used in the DSM-I to amplify the diagnosis of any "psychiatric disorder, " with clinical manifestations which fulfill the criteria of "psychosis."



        The second consensus-based classification with a description of its diagnostic terms was the DSM-II (41), introduced in 1968. It was based on the eighth revision of the International Classification of Diseases (ICD-8) of the World Health Organization (37), with a glossary of definitions added to the classification by the American contributors.

        In the DSM-II (41), mental disorders are divided into two (or three with the inclusion of "mental retardation") classes of (one class), and "neuroses," illness, i.e., "psychoses" "personality disorders, " and "other non-psychotic mental disorders" (other class). Included among the "psychoses" are "organic conditions" ("senile and presenile dementia," "alcoholic psychoses; " and "psychoses associated with intracranial infection, other cerebral conditions, and other physical conditions"), "affective psychoses," "schizophrenia," and "paranoid states."

        "Psychosis," in the DSM-II (41), is defined as a mental disorder in which mental functioning is impaired to the degree that it interferes with patient's ability to meet ordinary demands of life and recognize reality. Hallucinations and delusions may distort perceptions; alterations of mood may affect capacity to respond appropriately; and deficits in perception, language and memory may interfere with grasping situations effectively. In "affective psychoses," it is the disorder of mood, either extreme depression or extreme elation, which dominates mental life and is responsible for patient's loss of contact with the environment. In "schizophrenia," characteristic disturbances of thinking, mood and behavior dominate. The disturbances of perception and thinking are marked by hallucinations and alterations of concept formation, misinterpretations, and delusions. Corollary mood changes include ambivalent, constricted and inappropriate emotional responsiveness, and loss of empathy with others. Behavior may be withdrawn, regressive or bizarre. In "paranoid states," a delusion, generally persecutory or grandiose, is the essential abnormality, and the disturbances in mood, behavior, and thinking, including hallucinations, are secondary to this primary pathology. "Organic conditions" can be classified as "psychosis" only, if the patient is "psychotic" during the episode in which the diagnostic evaluation is made.



        The first consensus-based classification of the World Health Organization (38) with a description of its diagnostic terms was the mental disorders section of the 9th revision of the International Classification of Diseases (ICD-9) published in 1977. It is based on the division between "psychotic disorders" and "non psychotic disorders" introduced in the ICD-8 (37) and adopted in the DSM-II (41). The definition of "psychosis" was also adopted in the ICD-9 (38) from DSM-II (41).

        In variance with DSM-II (41), there is a clear separation of "organic" and "non-organic psychoses" in the ICD-9 (38) with the "organic syndromes" characterized by "impairment of orientation memory, comprehension, calculation, learning capacity, and judgement." Other organic features include "shallowness and lability of affect, persistent disturbance of mood, lowering of ethical standards, exaggeration of old and emergence of new personality traits, and diminished capacity for independent decisions." The term "delirium" defines one set of "organic psychoses" in which the "characteristic features" of "organicity" are overshadowed by "clouded consciousness, confusion, disorientation, delusions, illusions and vivid hallucinations"; and the term, "dementia," defines another set of "organic psychoses," which are chronic, progressive, and, if untreated, irreversible. While the definition of "affective psychoses" and of "paranoid states" are the same in the ICD-9 (38) and DSM-II (41), the scope of "other nonorganic psychoses" is restricted in the ICD-9 (38) to a small group of psychotic conditions which are "largely or entirely attributable to recent life experiences." The definition of "schizophrenic psychoses" is also changed to include Kurt Schneider's (49) "first rank symptoms." Thus, "schizophrenic psychoses" are defined in the ICD-9 (39) as a group of "psychoses" with a "fundamental disturbance of personality, a characteristic distortion of thinking, a sense of being controlled by alien forces, delusions which may be bizarre, disturbed perceptions, abnormal affect, and autism." In "schizophrenic psychoses," the "disturbance of personality" involves those "basic functions" which give each person a "feeling of individuality, uniqueness, and self-direction." The most "intimate thoughts, feelings and acts are often felt to be known to, or shared by others," and explanatory delusions may develop to the effect that natural or supernatural forces are at work to influence "thoughts and actions" in ways that are often "bizarre." "Hallucinations," especially of hearing, are common and may comment on or address the patient.



        In 1980, DSM-II (41) was replaced by DSM-IIIT (42), the first consensus-based classification with a multiaxial evaluation and operationalized diagnostic criteria. In DSM-III (42) all traditional dichotomies, e.g., "organic" versus "functional," "psychotic" versus "neurotic," are dismissed, and psychiatric syndromes are assigned to one of 15 categories of disease. All the different syndromes in three of these categories, i.e., "schizophrenic disorders," "paranoid disorders" and "psychotic disorders not elsewhere classified”; and some of the syndromes in two of the other categories, i.e., "organic mental disorders" and "affective disorders," qualify for "psychotic disorders."

        In DSM-III (42) the term "psychotic" is used to describe a patient at a given time, or a mental disorder in which at some time during its course all patients with the disorder evaluate incorrectly the accuracy of their perceptions and thoughts and make incorrect inferences about external reality, even in the face of contrary evidence. However, the term "psychotic" does not apply to "minor distortions of reality" that involves matters of relative judgement, but "gross impairment of reality testing" and the "creation of new reality." Thus, a depressed person who underestimates his/her achievements would not qualify for "psychotic," whereas one who believes he/she caused a natural catastrophe would qualify for it. Direct evidence of "psychotic behavior" is the presence of either "delusions" or "hallucinations" without insight into their pathological nature and/or "grossly disorganized behavior" from which a reasonable inference can be made that reality testing is markedly disturbed.

        In 1987 DSM-III (42) was replaced by DSM-III-R (43) with some minor modifications relevant to "psychotic disorders," e.g., the diagnostic term of "schizophrenic disorders" was replaced by the diagnostic term "schizophrenia," of "paranoid disorders" by "delusional (paranoid) disorder," of "shared paranoid disorder" by "induced psychotic disorder," of "affective disorders" by "mood disorders."


ICD-10 and DSM-IV

        The traditional division between "psychosis" and "neurosis" is dismissed also in the ICD-10 (39), introduced in 1992, to replace ICD-9 (38). The term "psychotic " has been retained in the ICD-10 (39) only as a convenient descriptive term which simply indicates the presence of certain "symptoms," such as "hallucinations," "delusions," "gross excitement and overactivity," "marked psychomotor retardation" and "catatonic behavior" in some of the psychiatric disorders. Nevertheless, it is also used in the diagnosis of a newly introduced category of illness, "acute and transient psychotic disorders," in which "psychotic symptoms" are the prevailing feature of the clinical picture.

        Similar to ICD-10 (39), in the DSM-IV (44), introduced in 1994, the diagnosis of "psychosis" is no longer based on the "severity of the functional impairment," i.e., on… "gross interference with the capacity to meet ordinary demands of life," but on the presence of certain "symptoms." Included among these symptoms are "delusions" and "hallucinations" with the "hallucinations occurring in the absence of insight into their pathological mature," "prominent hallucinations" which are perceived by the patient as "hallucinatory experiences" and some other "positive symptoms," such as "disorganized speech," and "grossly disorganized or catatonic behavior."


Diagnostic Criteria: Past and Present

        There has been a gradual shift in emphasis in the diagnostic criteria of "psychosis." While in the past, i.e., prior to the introduction of the DSM-III (42), diagnostic criteria of "psychosis" were based on the degree of the "severity" of the clinical manifestations, and on the interference of the manifestations with social adaptation, today, diagnostic criteria of "psychoses" are based on the presence of certain "psychopathological symptoms," and on the "psychotic behavior" displayed.

        For well over 50 years in Campbell's (47, 48) "psychiatric dictionary" the "psychoses" were differentiated from the other psychiatric disorders and especially from the "psychoneuroses" by one or more of the following five variables (47, 48): (a) "severity" (more severe, intense and disruptive), (b) "degree of withdrawal" (less able to maintain effective object relationships), (c) "affectivity" (emotions are qualitatively different from normal or exaggerated quantitatively), (d) "intellect" (language and thinking disturbed, judgement fails, hallucinations and delusions appear) and (e) "regression" (generalized failure of functioning with falling back to early behavioral levels). Other frequently used variables in the differentiation of the "psychoses" from the "psychoneuroses" were "insight" and "sociability" (lost in "psychoses" and retained in "psychoneuroses"), "personality" (wholly involved in "psychoses" and partially involved in "psychoneuroses") and "unconscious processes" (verbally expressed in "psychoses" and symbolically expressed in "psychoneuroses") (50).

        In current diagnostic manuals "psychotic behavior" 'is detected by the presence of one or more of the following "psychopathological symptoms": "hallucinations, "formal thought disorder" (disorganized or odd speech), "delusions" (including "disturbances of ego integrity," such as "thought insertion," "thought withdrawal," "feelings of being controlled"), "disturbances of affect" (flat /inappropriate), "avolition / apathy," "alogia," "disorganized behavior," '"catatonic motor behavior" and "depersonalization / derealization." Since the disorders which qualify for "psychosis," and in which "psychotic behavior" may be displayed, are differentiated from each other by "operationalized diagnostic criteria" which may or may not be based on the symptoms which signal "psychosis," "psychotic behavior" today is perceived "as a symptom of many psychiatric disorders" (51).


Concluding Remarks

        Since the time of the introduction of the term "psychosis" for the separation of "psychiatric disorders" from "neurological disorders" (8) well over 150 years passed. During this time the "concept of psychosis" has become restricted from a generic term for "psychiatric disorders," to "a symptom present in many psychiatric disorders" (51). Recently a set of "psychopathological symptoms" have been identified which signal the presence of "psychosis" regardless of the underlying disorder in which the "psychotic behavior" is displayed. Since all the "psychotic symptoms" identified represent a different aspect in the pathology in the "processing of mental events" in the brain (52), "psychotic behavior" with the "diagnostic criteria of psychosis" may provide suitable end points for neuropsychopharmacological research in the study of the relationship between "signal transduction" (53) and "processing of mental events" in the central nervous system.



1. Cullen W. First Lines in the Practice of Physic. Edinburgh, UK: C. Elliot; 1788.

2. Pichot P. A Century of Psychiatry. Paris, France: Roger Dacosta; 1983:28–40.

3. Garrison FH. An introduction to the History of Medicine. 4th ed. Philadelphia, Pa: Saunders; 1929:357–8.

4. Littre E. Dictionnaire de la Langue Française. Paris, France: Hachette & Cie; 1877.

5. Reil JC. Rhapsodien ueber die Anwendung Psychischen Kurmethode auf Geisteszerruetungen. Halle, Germany: Curt; 1803.

6. Heinroth JC. Lehrbuch der Stoerungen des Seelenlebens. Leipzig, Germany: Vogel; 1818.

7. Ban TA. Nosology in the teaching of psychiatry. J Bras Psiquiatr. 2000;49:39–49.

8. Feuchsterleben E. Lehrbuch der Aerztlichen Seelenkunde. Vienna, Austria: Carl Gerold; 1845.

9. Ban TA., Ucha Udabe R. Clasificación de las Psicosis. Buenos Aires, Argentina: Salerno; 1995:21–3.

10. Esquirol JED. Des Maladies Mentales Considérées sous les Rapports Médical, Hygiénique et Médico-légal. Paris, France: JP Baillière; 1838.

11. Griesinger W. Die Pathologie und Thérapie der Psychischen Krankheiten. Braunschweig, Germany: Wreden; 1845.

12. Bayle ALJ. Recherches sur I'Arachnitis Chronique Considérée Comme Cause d'Aliénation Mentale. Paris, France: Gabon; 1822.

13. Griesinger W. Die Pathologie und Thérapie der Psychischen Krankheiten. 2nd ed. Stuttgart, Germany: Krabbe; 1861.

14. Guislain J. Traité des Phrénopathies. Brussels, Belgium: Etablissement Encyclographique; 1833.

15. Marx OM. William Griesinger and the history of psychiatry: a reassessment. Bull Hist Med. 1972;6:519–44.

16. Morel BA. Traité de Dégénérescences Physiques, intellectuelles et Morales de l'Espèce Humaine. Paris, France: JP Baillière; 1857.

17. Moebius JP. Abriss der Lehie von den Nervenkrankheiten. Leipzig, Germany: Barth; 1893.

18. Faraone SV., Tsuang MT., Tsuang DW. Genetics of Mental Disorders. New York, NY: The Guilford Press; 1999:145–6.

19. Petronis A., Kennedy JL. Unstable genes - unstable mind. Am J Psychiatry. 1995;152:164–72.

20. Freud S. The Problems of Anxiety. New York, NY: WW Norton; 1936.

21. Kraepelin E. Lehrbuch der Psychiatrie. 6th ed. Leipzig, Germany: Barth; 1899.

22. Moebius JP. Ueber den physiologischen Schwachsinn des Weibes. Halle, Germany: Marhold; 1900.

23. Bonhoeffer K. Zur Frage der exogenen Psychosen. Zentralbl Nervenheilkd. 1909;32:499–505.

24. Wimmer A. Psykogene Sindssygdomsformer. Copenhagen, Denmark: Gad; 1916.

25. Jaspers K. Eifersuchtswahn: Entwicklung einer Persoenlichkeit oder Prozess. Z Gesamte Neurol Psychiatr. 1910;1:567–637.

26. Jaspers K. Allgemeine Psychopatoiogie. Heidelberg, Germany: Springer; 1913.

27. Jaspers K. General Psychopathology. Hoenig J, Hamilton MW, translator. Manchester, UK: Manchester University Press; 1963.

28. Schneider K. XX. Klinische Psychopathologie. Stuttgart, Germany: Thierne; 1950.

29. Bleuler E. Dementia Praecox oder Gruppe der Schizophrenien. Leipzig, Germany: Deuticke; 1911.

30. Fish FJ. XX. Clinical Psychopathology. Bristol, UK: Wright; 1967.

31. Petho B., Ban TA., Kelemen A., et al. DCR Budapest-Nashville in the diagnosis and classification of functional psychoses. Psychopathology. 1988;21:153–240.

32. Leonhard K. Aufteilung der endogenen Psychosen. Berlin, Germany: Akademie; 1957.

33. Astrup C. The Chronic Schizophrenias. Oslo, Norway: Universitetsforlaget; 1979.

34. Gaupp R. Die wissenschaftliche Bedeutung des Falles Wagner. Munch Med Wochenschr. 1914;61:633–7.

35. Kretschmer E. XX. Der sensitive Beziehungsvvahn. Berlin, Germany: Springer; 1927.

36. Stromgren E. Psychogenic psychoses. In: Hirsch SR, Shepherd M, eds. Themes and Variations in European Psychiatry. Charlottesville, Va: University Press of Virginia; 1974:97–117.

37. World Health Organization. International Classification of Diseases. 8th Revision. Geneva, Switzerland: World Health Organization; 1968.

38. World Health Organization. International Classification of Diseases. 9th Revision. Geneva, Switzerland: World Health Organization; 1977:177–213.

39. World Health Organization. The ICD-10 Classification of Mental and Behavioral Disorders. Clinical descriptions and diagnostic guidelines. Geneva, Switzerland: World Health Organization; 1992.

40. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. Washington, DC: American Psychiatric Association; 1952.

41. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 2nd ed. Washington, DC: American Psychiatric Association; 1968.

42. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 3rd ed. Washington, DC: American Psychiatric Association; 1980.

43. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 3rd ed, revised. Washington, DC: American Psychiatric Association; 1987.

44. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 4th ed. Washington, DC: American Psychiatric Association; 1994.

45. Ban TA. From DSM-III to DSM-IV: progress or standstill. In: Franzek E, Ungvari GS, Ruther E, Beckmann H, eds. Progress in Differentiated Psychopathology. Würzburg, Germany: International Wernicke-Kleist-Leonhard Society; 2000.

46. Billings EG. A Handbook of Elementary Psychobiology and Psychiatry (Part 1. Psychobiology). New York, NY: The Macmillan Company; 1939:3–22.

47. Campbell RJ. Psychiatric Dictionary. Oxford, UK: Oxford University Press; 1940.

48. Campbell RJ. Psychiatric Dictionary. 7th ed. Oxford, UK: Oxford University Press; 1996.

49. Schneider K. Primaere und sekundaere Symptomen bei Schizophrénie. Fortschr Neurol Psychiatr. 1957;25:487–90.

50. Thakurdas H., Thakurdas L. Dictionary of Psychiatry. Revised byThakurdas B. Lancaster, UK: MTP Press; 1979.

51. National Institute of Mental Health Molecular Genetic Initiative. Diagnostic Instrument for Genetic Studies Training Manual. Version 2.0. Washington, DC: National Institute of Mental Health; 1997:35–46.

52. Wernicke C. Grundriss der Psychiatrie Klinische Vorlesungen. Leipzig, Germany: Thieme; 1900.

53. Bloom F. Personal perspectives. Am Coll Neuropsychopharmacol Bull. 2001;7:4–8.