Historical Background

The conceptual history of schizophrenia dates back to the end of the nineteenth century, and to the description of dementia praecox by Emil Kraepelin. Other major influences on the current concept of schizophrenia are those of Bleuler, Schneider, Jaspers and Hughlings Jackson.

In the fifth edition of his textbook [6], Emil Kraepelin established a classification of mental disorders which was based upon the medical model. His goal was to delineate disease entities having a common aetiology, symptomatology, course and outcome. One of these entities he called dementia praecox, because it started early on in life and almost invariably led to psychic impairment. Characteristic symptoms included hallucinations, experiences of influence, disturbances in attention, comprehension and the flow of thought, affective flattening and catatonic symptoms. The aetiology was endogenous,

Schizophrenia, Second Edition. Edited by Mario Majand Norman Sartorius. © 2002 John Wiley & Sons Ltd.

that is, the disorder arose out of inner causes. Dementia praecox was separated from manic-depressive disorder and from paranoia on the basis of symptom and course criteria. Kraepelin distinguished three forms of the disorder: hebephrenic, catatonic and paranoid.

Eugen Bleuler [7] acknowledged that ''the concept of dementia praecox comes from Kraepelin and that the grouping and identification of individual symptoms is almost entirely due to him''. Bleuler retained Kraepelin's separation of the disorder from manic-depressive illness and gave the disorder its present name of schizophrenia. In his view, the course of schizophrenia was variable, but probably never reached restitutio ad integrum. In fact, Bleuler focused on ''fundamental'' and ''primary'' signs and symptoms rather than on course and outcome. In particular, he emphasized the presence of a dissociation (Spaltung) of mental functions as the essential characteristic of the disorder. The main aspect of dissociation was a loosening of associations. Other defining features of the disorder were affective blunting and inappropriate affect, ambivalence, autism and disordered attention. For Bleuler, schizophrenia was not a unitary disease. The ''group of schizophrenias'' subsumed multiple disorders that shared a number of clinical features but differed in aetiology and pathogenesis. In particular, it included a subgroup designated ''simple schizophrenia'', in which many of the prominent features of the disorder were absent. Since schizophrenia encompassed both severe and mild forms, the scope of the concept was much broader than Kraepelin's.

The writings of Karl Jaspers had a lasting influence on psychiatric nosology, and in particular on the diagnosis of schizophrenia. In his Allgemeine Psychopathologie [8], Jaspers considered that psychopathological symptoms were organized in layers or levels, from the more ''profound'' to the more ''superficial''. The most profound level was represented by organic symptoms, then came schizophrenic, affective and neurotic symptoms, and finally symptoms related to personality disorders. When symptoms from different levels were present simultaneously, diagnosis was determined by those symptoms that belonged to the most profound level. One of the major consequences of this system, which was to become known under the name ''Jaspersche Schichtenregel'' (hierarchical rule of levels), was that whenever schizophrenic and affective symptoms were present at the same time, clinicians opted for a diagnosis of schizophrenia.

For Kurt Schneider, psychiatric diagnosis was based fundamentally on the clinical picture and not on the course. In his Klinische Psychopathologie [9], Schneider distinguished between psychical abnormalities and diseases. Diseases were subdivided into psychoses with demonstrable organic aetiology, cyclophrenia and schizophrenia. In his description of psychopatholog-ical phenomena, Schneider differentiated between abnormal ''experiences'' and abnormal ''expressions''. Abnormal experiences refer to disturbances in perceptions, sensations, feelings, impulses and volition. Abnormal expressions concern disturbances in language, writing, mimic and movement. For Schneider, the diagnosis of schizophrenia had to rely essentially on abnormal experiences, with in particular a number of specified experiences that he designated as ''first-rank symptoms'', and which he considered to be pathognomonic of the disorder.

Hughlings Jackson [10] applied the terms ''positive'' and ''negative'' to delineate primary from secondary neurological phenomena. According to Jackson, negative symptoms result directly from damage to brain areas that are responsible for the production of human behaviour, while positive symptoms reflect brain processes that are disinhibited or released by the damaged brain. In 1974, Strauss et al [11] proposed to distinguish two symptom profiles in schizophrenia: positive symptoms and negative symptoms. Positive symptoms are defined by the presence of abnormal features such as hallucinations, delusions and disorganized thinking. Negative symptoms are defined by the absence of normal functions, and are characterized by symptoms such as blunted affect, emotional withdrawal and cognitive deficits. In 1980, Crow [12] proposed a typology of schizophrenia based on the positive and negative dichotomy.

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