Editing Dementia praecox (section)

===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.{{sfn|Noll|2007a|p=[https://books.google.com/books?id=jzoJxps189IC&pg=PR14 xiv]}} He described the method in his posthumously published memoir:
{{blockquote|... 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.<ref>{{harvnb|Kraepelin|1987|p=61}}</ref>}}

The fourth edition of his textbook, {{lang|de|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.{{sfn|Noll|2007a|p=[https://books.google.com/books?id=jzoJxps189IC&pg=PR14 xiv]}}

In the March 1896 fifth edition of {{lang|de|Psychiatrie}}, Kraepelin expressed confidence that his [[clinical trial|clinical]] [[scientific method|method]], involving analysis of both [[qualitative research|qualitative]] and [[quantitative research|quantitative]] data derived from long term observation of patients, would produce reliable diagnoses including prognosis:
{{blockquote|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.<ref>{{harvnb|Kraepelin|1896|p=v}} quoted in {{harvnb|Noll|2007a|p=[https://books.google.com/books?id=jzoJxps189IC&pg=PR14 xiv]}}</ref>}}
In this edition dementia praecox is still essentially hebephrenia, and it, dementia paranoides and catatonia are described as distinct psychotic disorders among the "metabolic disorders leading to dementia".<ref>{{harvnb|Noll|2007a|p=[https://books.google.com/books?id=jzoJxps189IC&pg=PR14 xiv]}}</ref>