Is Dementia Praecox the Same as Dementia?

In a word, no, but its history is fascinating.

Dementia praecox (a “premature dementia” or “precocious madness”) refers to a chronic, deteriorating psychotic disorder characterized by rapid cognitive disintegration, usually beginning in the late teens or early adulthood. It is a term first used in 1891 in this Latin form by Arnold Pick (1851–1924), a professor of psychiatry at the German branch of Charles University in Prague.[1] His brief clinical report described the case of a person with a psychotic disorder resembling hebephrenia (see below). It was popularized by German psychiatrist Emil Kraepelin (1856–1926) in 1893, 1896 and 1899 in his first detailed textbook descriptions of a condition that would eventually be reframed into a substantially different disease concept and relabeled asschizophrenia. Kraepelin, regarding the major psychoses as naturally occurring disease entities, reduced the complex psychiatric taxonomies of the nineteenth century by dividing them into two classes: manic depressive psychosis or dementia praecox. This division is commonly referred to as the Kraepelinian dichotomy and it has had a significant and fundamental impact on twentieth-century psychiatry, though has also been questioned.[2]

 

An article by Eugen Bleuler on dementia praecox (1911)

Dementia praecox (a “premature dementia” or “precocious madness”) refers to a chronic, deteriorating

The primary disturbance in dementia praecox was said to be not one of mood, but of thinking or cognition. Cognitive disintegration refers to a disruption in cognitive or mental functioning such as in attention, memory, and goal-directed behavior. Kraepelin contrasted this with manic-depressive psychosis, in which he included not just what would be termed bipolar disorder today but also other forms of mood disorder, including major depressive disorder. However, Kraepelin himself noted cases inbetween and eventually accepted that it was not possible to distinguish his categories on the basis of cross-sectional symptoms.[3] Indeed, a mixed diagnosis of schizoaffective disorder has also developed.

From the outset, dementia praecox was viewed by Kraepelin as a progressively deteriorating disease from which no one recovered. The three terms that Kraepelin used to refer to the end state of the disease were “Verblödung” (deterioration),Schwachsinn (mental weakness) or Defekt (defect). Although “dementia” is part of the name of the disease, Kraepelin did not intend it to be similar to senile dementia and rarely used this term to refer to the end state of the disease. However, by 1913, and more explicitly by 1920, Kraepelin admitted that although there seemed to be a residual cognitive defect in most cases, the prognosis was not as uniformly dire as he had stated in the 1890s. Still, he regarded it as a specific disease concept that implied incurable, inexplicable madness.

History

the history of dementia praecox is really that of psychiatry as a whole – —Adolf Meyer[4

First use of the term

Benedict Augustin Morel (1809-1873)

The term dementia is an ancient term which has been in use since at least the time of Lucretiusin 50 B.C.E. where it meant “being out of one’s mind”.[5] Until the seventeenth century dementia referred to states of cognitive and behavioural deterioration leading to psychosocial incompetence. This condition could be innate or acquired and the concept had no reference to a necessarily irreversible condition. It is the concept in this popular notion of psychosocial incapacity that forms the basis for the idea of legal incapacity.[6] By the eighteenth century, at the period when the term entered into European medical discourse, clinical concepts were added to the vernacular understanding such that dementia was now associated with intellectual deficits arising from any cause and at any age.[7] By the end of the nineteenth century the modern ‘cognitive paradigm’ of dementia was taking root.[8] This holds that dementia is understood in terms of criteria relating to aetiology, age and course which excludes former members of the family of the demented such as adults with acquired head trauma or children with cognitive deficits. Moreover, it was now understood as an irreversible condition and a particular emphasis was placed on memory loss in regard to the deterioration of intellectual functions.[9]

The term démence précoce was used in passing to describe the characteristics of a subset of young mental patients by the French physician Bénédict Augustin Morel in 1852 in the first volume of his Études cliniques.[10] and the term is used more frequently in his textbook Traité des maladies mentales which was published in 1860.[11] Morel, whose name will be forever associated with religiously inspired concept of degeneration theory in psychiatry, used the term in a descriptive sense and not to define a specific and novel diagnostic category. It was applied as a means of setting apart a group of young men and women who were suffering from “stupor.”[12] As such their condition was characterised by a certain torpor, enervation, and disorder of the will and was related to the diagnostic category of melancholia. He did not conceptualise their state as irreversible and thus his use of the term dementia was equivalent to that formed in the eighteenth century as outlined above.[13]

While some have sought to interpret, if in a qualified fashion, the use by Morel of the term démence précoce as amounting to the “discovery” of schizophrenia,[12] others have argued convincingly that Morel’s discriptive use of the term should not be considered in any sense as a precursor to Kraepelin’s dementia praecox disease concept.[9] This is due to the fact that their concepts of dementia differed significantly from each other, with Kraepelin employing the more modern sense of the word and that Morel was not describing a diagnostic category. Indeed, until the advent of Pick and Kraepelin, Morel’s term had vanished without a trace and there is little evidence to suggest that either Pick or indeed Kraepelin were even aware of Morel’s use of the term until long after they had published their own disease concepts bearing the same name.[14] As Eugène Minkowski succinctly stated, ‘An abyss separates Morel’s démence précoce from that of Kraepelin.’[15]

Morel described several psychotic disorders that ended in dementia, and as a result he may be regarded as the first alienist or psychiatrist to develop a diagnostic system based on presumed outcome rather than on the current presentation of signs and symptoms. Morel, however, did not conduct any long-term or quantitative research on the course and outcome of dementia praecox (Kraepelin would be the first in history to do that) so this prognosis was based on speculation. It is impossible to discern whether the condition briefly described by Morel was equivalent to the disorder later called dementia praecox by Pick and Kraepelin.

The time component

Karl Ludwig Kahlbaum 1828-1899)

Psychiatric nosology in the nineteenth-century was chaotic and characterised by a conflicting mosaic of contradictory systems.[16] Psychiatric disease categories were based upon short-term and cross-sectional observations of patients from which were derived the putative characteristic signs and symptoms of a given disease concept.[17]The dominant psychiatric paradigms which gave a semblance of order to this fragmentary picture were Morelian degeneration theory and the concept of “unitary psychosis” (Einheitspsychose).[18] This latter notion, derived from the Belgian psychiatrist Joseph Guislain (1797–1860), held that the variety of symptoms attributed to mental illness were manifestations of a single underlying disease process.[19] While these approaches had a diachronic aspect they lacked a conception of mental illness that encompassed a coherent notion of change over time in terms of the natural course of the illness and based upon an empirical observation of changing symptomatology.[20]

In 1863, the Danzig based psychiatrist, Karl Ludwig Kahlbaum (1828–1899), published his text on psychiatric nosology Die Gruppierung der psychischen Krankheiten (The Classification of Psychiatric Diseases).[21] Although with the passage of time this work would prove profoundly influential, when it was published it was almost completely ignored by German academia despite the sophisticated and intelligent disease classification system which it proposed.[22] In this book Kahlbaum categorized certain typical forms of psychosis (vesania typica) as a single coherent type based upon their shared progressive nature which betrayed, he argued, an ongoing degenerative disease process.[23] For Kahlbaum the disease process of vesania typica was distinguished by the passage of the sufferer through clearly defined disease phases: a melancholic stage; a manic stage; a confusional stage; and finally a demented stage.[24]

In 1866 Kahlbaum became the director of a private psychiatric clinic in Görlitz (Prussia, today Saxony, a small town near Dresden). He was accompanied by his younger assistant, Ewald Hecker (1843–1909), and during a ten-year collaboration they conducted a series of research studies on young psychotic patients that would become a major influence on the development of modern psychiatry.

Together Kahlbaum and Hecker were the first to describe and name such syndromes as dysthymiacyclothymiaparanoia,catatonia, and hebephrenia.[25] Perhaps their most lasting contribution to psychiatry was the introduction of the “clinical method” from medicine to the study of mental diseases, a method which is now known as psychopathology.

When the element of time was added to the concept of diagnosis, a diagnosis became more than just a description of a collection of symptoms: diagnosis now also defined by prognosis (course and outcome). An additional feature of the clinical method was that the characteristic symptoms that define syndromes should be described without any prior assumption of brain pathology (although such links would be made later as scientific knowledge progressed). Karl Kahlbaum made an appeal for the adoption of the clinical method in psychiatry in his 1874 book on catatonia. Without Kahlbaum and Hecker there would be no dementia praecox.[26]

Upon his appointment to a full professorship in psychiatry at the University of Dorpat (now TartuEstonia) in 1886, Kraepelin gave an inaugural address to the faculty outlining his research programme for the years ahead. Attacking the “brain mythology” of Meynert and the positions of Griesinger and GuddenKraepelin advocated that the ideas of Kahlbaum, who was then a marginal and little known figure in psychiatry, should be followed. Therefore, he argued, a research programme into the nature of psychiatric illness should look at a large number of patients over time to discover the course which mental disease could take.[27]It has also been suggested that Kraepelin’s decision to accept the Dorpat post was informed by the fact that there he could hope to gain experience with chronic patients and this, it was presumed, would facilitate the longitudinal study of mental illness.[28]

The quantitative component

Understanding that objective diagnostic methods must be based on scientific practice, Kraepelin had been conducting psychological and drug experiments on patients and normal subjects for some time when, in 1891, he left Dorpat and took up a position as professor and director of the psychiatric clinic at Heidelberg University. There he established a research program based on Kahlbaum’s proposal for a more exact qualitative clinical approach, and his own innovation: a quantitative approach involving meticulous collection of data over time on each new patient admitted to the clinic (rather than only the interesting cases, as had been the habit until then).

Kraepelin believed that by thoroughly describing all of the clinic’s new patients on index cards, which he had been using since 1887, researcher bias could be eliminated from the investigation process.[29] He described the method in his posthumously published memoir:

… after the first thorough examination of a new patient, each of us had to throw in a note [in a "diagnosis box"] with his diagnosis written on it. After a while, the notes were taken out of the box, the diagnoses were listed, and the case was closed, the final interpretation of the disease was added to the original diagnosis. In this way, we were able to see what kind of mistakes had been made and were able to follow-up the reasons for the wrong original diagnosis.[30]

The fourth edition of his textbook, Psychiatrie, published in 1893, two years after his arrival at Heidelberg, contained some impressions of the patterns Kraepelin had begun to find in his index cards. Prognosis (course and outcome) began to feature alongside signs and symptoms in the description of syndromes, and he added a class of psychotic disorders designated “psychic degenerative processes”, three of which were borrowed from Kahlbaum and Hecker: dementia paranoides (a degenerative type of Kahlbaum’s paranoia, with sudden onset), catatonia (per Kahlbaum, 1874) and dementia praecox, (Hecker’s hebephrenia of 1871). Kraepelin continued to equate dementia praecox with hebephrenia for the next six years.[29]

In the March 1896 fifth edition of Psychiatrie, Kraepelin expressed confidence that his clinical method, involving analysis of bothqualitative and quantitative data derived from long term observation of patients, would produce reliable diagnoses including prognosis:

What convinced me of the superiority of the clinical method of diagnosis (followed here) over the traditional one, was the certainty with which we could predict (in conjunction with our new concept of disease) the future course of events. Thanks to it the student can now find his way more easily in the difficult subject of psychiatry.[31]

In this edition dementia praecox is still basically hebephrenia, and it, dementia paranoides and catatonia are described as distinct psychotic disorders among the “metabolic disorders leading to dementia”.[32]

Kraepelin’s influence on the next century

Emil Kraepelin c. 1920.

In the 1899 (6th) edition of Psychiatrie, Kraepelin established a paradigm for psychiatry that would dominate the following century, sorting most of the recognized forms of insanity into two major categories: dementia praecox and manic-depressive illness. Dementia praecox was characterized by disordered intellectual functioning, whereas manic-depressive illness was principally a disorder of affect or mood; and the former featured constant deterioration, virtually no recoveries and a poor outcome, while the latter featured periods of exacerbation followed by periods of remission, and many complete recoveries. The class, dementia praecox, comprised the paranoid, catatonic and hebephrenic psychotic disorders, and these forms are still found today in theDSM-IV-TR‘s paranoid, catatonic and disorganized types of schizophrenia. The ICD-10still uses “hebephrenic” to designate the third type.[33] These subtypes may be dropped from the next edition of the DSM, DSM-V, due to be published in May 2013.[34]

Change in prognosis

In the seventh, 1904, edition of Psychiatrie, Kraepelin accepted the possibility that a small number of patients may recover from dementia praecox. Eugen Bleuler reported in 1908 that in many cases there was no inevitable progressive decline, there was temporary remission in some cases, and there were even cases of near recovery with the retention of some residual defect. In the eighth edition of Kraepelin’s textbook, published in four volumes between 1909 and 1915, he described eleven forms of dementia, and dementia praecox was classed as one of the “endogenous dementias”. Modifying his previous more gloomy prognosis in line with Bleuler’s observations, Kraepelin reported that about 26% of his patients experienced partial remission of symptoms. Kraepelin died while working on the ninth edition of Psychiatrie with Johannes Lange (1891–1938), who finished it and brought it to publication in 1927.[35]

Etiology

Though his work and that of his research associates had revealed a role for heredity, Kraepelin realized nothing could be said with certainty about the etiology of dementia praecox, and he left out speculation regarding brain disease or neuropathology in his diagnostic descriptions. Nevertheless, from the 1896 edition onwards Kraepelin made clear his belief that poisoning of the brain, “autointoxication”, probably by sex hormones, may underlie dementia praecox – a theory also entertained by Eugen Bleuler. Both theorists insisted dementia praecox is a biological disorder, not the product of psychological trauma. Kraepelin, recognizing dementia praecox in Chinese, Japanese, Tamil and Malay patients, suggested in the eighth edition of Psychiatrie that, “we must therefore seek the real cause of dementia praecox in conditions which are spread all over the world, which thus do not lie in race or in climate, in food or in any other general circumstance of life…”[36]

Treatment

Kraepelin had experimented with hypnosis but found it wanting, and disapproved of Freud’s and Jung’s introduction, based on no evidence, of psychogenic assumptions to the interpretation and treatment of mental illness. He argued that, without knowing the underlying cause of dementia praecox or manic-depressive illness, there could be no disease-specific treatment, and recommended the use of long baths and the occasional use of drugs such as opiates and barbiturates for the amelioration of distress, as well as occupational activities, where suitable, for all institutionalized patients. Based on his theory that dementia praecox is the product of autointoxication emanating from the sex glands, Kraepelin experimented, without success, with injections of thyroid, gonad and other glandular extracts.[36]

Use of term spreads

“Psychiatrists of Europe! Protect your sanctified diagnoses!” A satirizing cartoon by Emil Kraepelin based on a famous contemporary political painting.[2]

Kraepelin noted the dissemination of his new disease concept when in 1899 he enumerated the term’s appearance in almost twenty articles in the German-language medical press.[36] In the early years of the twentieth century the twin pillars of the Kraepelinian dichotomy, dementia praecox and manic depressive psychosis, were assiduously adopted in clinical and research contexts among the Germanic psychiatric community.[36] German-language psychiatric concepts were always introduced much faster in America (than, say, Britain) where émigré German, Swiss and Austrian physicians essentially created American psychiatry. Swiss-emigree Adolf Meyer (1866–1950), arguably the most influential psychiatrist in America for the first half of the 20th century, published the first critique of dementia praecox in an 1896 book review of the 5th edition of Kraepelin’s textbook. But it was not until 1900 and 1901 that the first three American publications regarding dementia praecox appeared, one of which was a translation of a few sections of Kraepelin’s 6th edition of 1899 on dementia praecox.

Adolf Meyer was the first to apply the new diagnostic term in America. He used it at the Worcester Lunatic Hospital in Massachusetts in the fall of 1896. He was also the first to apply Eugen Bleuler’s term “schizophrenia” (in the form of “schizophrenic reaction”) in 1913 at the Henry Phipps Psychiatric Clinic of the Johns Hopkins Hospital.

The dissemination of Kraepelin’s disease concept to the Anglo-phone world was facilitated in 1902 when Ross Diefendorf, a lecturer in psychiatry at Yale, published an adapted version of the sixth edition of the Lehrbuch der Psychiatrie. This was republished in 1904 and with a new version, based on the seventh edition of Kraepelin’s Lehrbuch appearing in 1907 and reissued in 1912.[37] Both dementia praecox (in its three classic forms) and “manic-depressive psychosis” gained wider popularity in the larger institutions in the eastern United States after being included in the official nomenclature of diseases and conditions for record-keeping at Bellevue Hospital in New York City in 1903. The term lived on due to its promotion in the publications of the National Committee on Mental Hygiene (founded in 1909) and the Eugenics Records Office (1910). But perhaps the most important reason for the longevity of Kraepelin’s term was its inclusion in 1918 as an official diagnostic category in the uniform system adopted for comparative statistical record-keeping in all American mental institutions, The Statistical Manual for the Use of Institutions for the Insane. Its many revisions served as the official diagnostic classification scheme in America until 1952 when the first edition of the Diagnostic and Statistical Manual:Mental Disorders, or DSM-I, appeared. Dementia praecox disappeared from official psychiatry with the publication of DSM-I, replaced by the Bleuler/Meyer hybridization, “schizophrenic reaction”.

Schizophrenia was mentioned as an alternate term for dementia praecox in the 1918 Statistical Manual. In both clinical work as well as research, between 1918 and 1952 five different terms were used interchangeably: dementia praecox, schizophrenia, dementia praecox (schizophrenia), schizophrenia (dementia praecox) and schizophrenic reaction. This made the psychiatric literature of the time confusing since, in a strict sense, Kraepelin’s disease was not Bleuler’s disease. They were defined differently, had different population parameters, and different concepts of prognosis.

The reception of dementia praecox as an accepted diagnosis in British psychiatry came more slowly, perhaps only taking hold around the time of World War I. There was substantial opposition to the use of the term “dementia” as misleading, partly due to findings of remission and recovery. Some argued that existing diagnoses such as “delusional insanity” or “adolescent insanity” were better or more clearly defined.[38] In France a psychiatric tradition regarding the psychotic disorders predated Kraepelin, and the French never fully adopted Kraepelin’s classification system. Instead the French maintained an independent classification system throughout the 20th century. After 1980, when DSM-III totally reshaped psychiatric diagnosis, French psychiatry began to finally alter its views of diagnosis to converge with the North American system. Kraepelin thus finally conquered France via America.

From dementia praecox to schizophrenia

Due to the influence of alienists such as Adolf Meyer, August Hoch, George Kirby, Charles Macphie Campbell, Smith Ely Jelliffe and William Alanson White, psychogenic theories of dementia praecox dominated the American scene by 1911. In 1925 Bleuler’s schizophrenia rose in prominence as an alternative to Kraepelin’s dementia praecox. When Freudian perspectives became influential in American psychiatry in the 1920s schizophrenia became an attractive alternative concept. Bleuler corresponded with Freud and was connected to Freud’s psychoanalytic movement,[39] and the inclusion of Freudian interpretations of the symptoms of schizophrenia in his publications on the subject, as well as those of C.G. Jung, eased the adoption of his broader version of dementia praecox (schizophrenia) in America over Kraepelin’s narrower and prognostically more negative one.

The term “schizophrenia” was first applied by American alienists and neurologists in private practice by 1909 and officially in institutional settings in 1913, but it took many years to catch on. It is first mentioned in The New York Times in 1925. Until 1952 the terms dementia praecox and schizophrenia were used interchangeably in American psychiatry, with occasional use of the hybrid terms “dementia praecox (schizophrenia)” or “schizophrenia (dementia praecox)”.

Diagnostic manuals

Editions of the Diagnostic and Statistic Manual of Mental Disorders since the first in 1952 had reflected views of schizophrenia as “reactions” or “psychogenic” (DSM-I), or as manifesting Freudian notions of “defense mechanisms” (as in DSM-II of 1969 in which the symptoms of schizophrenia were interpreted as “psychologically self-protected”). The diagnostic criteria were vague, minimal and wide, including either concepts that no longer exist or that are now labeled as personality disorders (for example, schizotypal personality disorder). There was also no mention of the dire prognosis Kraepelin had made. Schizophrenia seemed to be more prevalent and more psychogenic and more treatable than either Kraepelin or Bleuler would have allowed.

Conclusions

As a direct result of the effort to construct Research Diagnostic Criteria (RDC) in the 1970s that were independent of any clinical diagnostic manual, Kraepelin’s idea that categories of mental disorder should reflect discrete and specific disease entities with a biological basis began to return to prominence. Vague dimensional approaches based on symptoms—so highly favored by the Meyerians and psychoanalysts—were overthrown. For research purposes, the definition of schizophrenia returned to the narrow range allowed by Kraepelin’s dementia praecox concept. Furthermore, after 1980 the disorder was a progressively deteriorating one once again, with the notion that recovery, if it happened at all, was rare. This revision of schizophrenia became the basis of the diagnostic criteria in DSM-III (1980). Some of the psychiatrists who worked to bring about this revision referred to themselves as the “neo-Kraepelinians”.

  1. ^Hoenig 1995, p. 337.
  2. ^Greene 2007, p. 361.
  3. ^Berrios, Luque & Villagran 2003, p. 134.
  4. ^Sass 1994, p. [1].
  5. ^Berrios 1996, p. 172Malgorzata 2004, p. 2; Bourgeois 2005, p. 199Adams 1997, p. 183
  6. ^Berrios 1996, p. 172Berrios, Luque & Villagran 2003, p. 116
  7. ^Berrios, Luque & Villagran 2003, p. 116.
  8. ^Burns 2009, pp. 199-200.
  9. abBerrios, Luque & Villagran 2003, p. 117.
  10. ^Hoenig 1995, p. 337; Boyle 2002, p. 46. Berrios, Luque and Villagran contend in their 2003 article on schizophrenia that Morel’s first use dates to the publication in 1860 of Traité des maladies mentales (Berrios & Luque Villagran2003, p. 117;Morel 1860). Dowbiggin inaccurately states that Morel used the term on page 234 of the first volume of his 1852 publication Etudes cliniques (Dowbiggin 1996, p. 388; Morel 1852, p. 234). On page 235] Morel does refer to démence juvénile in positing that senility is not an age specific affliction and he also remarks that at his clinic he sees almost as many young people suffering from senility as old people (Morel 1852, p. 235). Also, as Hoenig accurately states, Morel uses the term twice in his 1852 text on pages 282 and 361 (Hoenig 1995, p. 337; Morel 1852, pp. 282,361). In the first instance the reference is made in relation to young girls of asthenic build who have often also suffered from typhoid. It is a description and not a diagnostic category (Morel 1852, p. 282). In the next instance the term is used to argue that the illness course for those who suffer mania does not normally terminate in an early form of dementia (Morel 1852, p. 361).
  11. ^Berrios & Luque Villagran2003, p. 117. The term Démence précoce is used by Morel once in his 1857 text Traité des dégénérescence physiques, intellectuelles, et morales de l’espèce humaine (Morel 1857, p. 391) and seven times in his 1860 book Traité des maladies mentales (Morel 1860, pp. 119279516526532536552).
  12. abDowbiggin 1996,
  13. ^Berrios, Luque & Villagran 2003, p. 118.
  14. ^ While Berrios, Luque and Villagran argue this point forcefully (Berrios, Luque & Villagran 2003, p. 117), others baldly state that Kraepelin was clearly inspired by Morel’s lead. Yet no evidence of this claim is offered. For example, Stone 2006, p. 1.
  15. ^ Quoted in Berrios, Luque & Villagran 2003, p. 117.
  16. ^Kraam 2008, p. 77; Jablensky 1999, p. 96; Scharfetter 2001, p. 34;Engstrom 2003, p. 27
  17. ^Noll 2007a, p. 145Hoenig 1995, pp. 337–8; Kraam 2009, p. 88
  18. ^Noll 2007a, p. 145Engstrom 2003, p. 27
  19. ^Noll 2007a, p. 145
  20. ^Noll 2007a, p. 242.
  21. ^Engstrom 2003, p. 263Pillmann & Marneros 2003, p. 163;Kahlbaum 1863
  22. ^Kraam 2009, p. 87.
  23. ^Noll 2007a, p. 242Pillmann & Marneros 2003, p. 163
  24. ^Kraam 2009, p. 105; Kahlbaum 1863, p. 135
  25. ^Porter 1999, p. 512.
  26. ^Hoenig 1995, pp. 337-8.
  27. ^Steinberger & Angermeyer 2001, pp. 297-327.
  28. ^Berrios 1996, p. 23.
  29. abNoll 2007a, p. xiv.
  30. ^Kraepelin 1987, p. 61
  31. ^Kraepelin 1896, p. v quoted in Noll 2007a, p. xiv
  32. ^Noll 2007a, p. xiv
  33. ^American Psychiatric Association 2000, p. 303.
  34. ^American Psychiatric Association 2011.
  35. ^Noll 2007a, pp. 126–7
  36. abcdNoll 2007a, p. 127.
  37. ^Dain 1980, pp. 34341 n. 38Diefendorf 1912, pp. 219–75
  38. ^Ion & Beer 2002a, pp. 285–304; Ion & Beer 2002b, pp. 419–31
  39. ^ Makari, George. Revolution in Mind: The Creation of Psychoanalysis, Harper Perenial: New York, 2008.