In 1886, after only eight years of training, he was appointed to a professorship at Dorpat (now Tartu in Estonia) and became the director of an eighty-bed University Clinic. There he was able to study and record many clinical histories in detail and "was led to consider the importance of the course of the illness with regard to the classification of mental disorders." Ten years later he announced that he had found a new way of looking at mental illness. He referred to the traditional view as "symptomatic" and to his view as "clinical."
Drawing on his long term research, and using the criteria of course, outcome and prognosis, he developed the concept of dementia praecox, which he defined as the "sub-acute development of a peculiar simple condition of mental weakness occurring at a youthful age." When he first introduced this concept as diagnostic entity in the fourth German edition of his Lehrbuch der Psychiatrie in 1893, it was placed among the degenerative disorders alongside, but separate from, katonia and dementia paranoides. At that time the concept corresponded by and large with Ewald Hecker's hebrephrenia. In the sixth edition of the Lehrbuch in 1899 all three of these clinical types are treated but as different expressions of one disease, dementia praecox.
Kraepelin postulated that there is a specific brain or other biological pathology underlying each of the major psychiatric disorders. Just as his laboratory discovered the pathologic basis of what is now known as Alzheimers disease, Kraepelin was confident that it would someday be possible to identify the pathologic basis of each of the major psychiatric disorders.
One of the cardinal principles of his method was the recognition that any given symptom may appear in virtually any one of these disorders; i.e. there is virtually no single symptom occurring in schizophrenia which cannot sometimes be found in manic-depression. What distinguishes each disease symptomatically (as opposed to the underlying pathology) is not any particular (pathognomonic) symptom or symptoms, but a specific pattern of symptoms. In the absence of a direct physiological or genetic test or marker for each disease, it is only possible to distinguish them by their specific pattern of symptoms. Thus, Kraepelin's system is a method for pattern recognition, not grouping by common symptoms.
Kraepelin also demonstrated specific patterns in the genetics of these disorders and specific and characteristic patterns in their course and outcome. Generally speaking, there tend to be more schizophrenics among the relatives of schizophrenic patients than in the general population, while manic-depression is more frequent in the relatives of manic-depressives.
He also reported a pattern to the course and outcome of these conditions. Kraepelin believed that schizophrenia had a deteriorating course in which mental function continuously (although perhaps erratically) declines, while manic-depressive patients experienced a course of illness which was intermittent, where patients were relatively symptom-free during the intervals which separate acute episodes. This led Kraepelin to name what we now know as schizophrenia, dementia praecox (the dementia part signifing the irreversible mental decline). It later became clear that dementia praecox did not necessarily lead to mental decline and so was renamed by Eugene Bleuler to correct the misnomer.
Kraepelin is credited with the classification of what was previously considered to be a unitary concept of psychosis, into two distinction forms:
In addition to his distinction between dementia praecox and manic-depression, Kraepelin should be credited with being the founder of modern scientific psychiatry, psychopharmacology and psychiatric genetics, according to the eminent psychologist H. J. Eysenck in his Encyclopedia of Psychology. Kraepelin postulated that psychiatric diseases are principally caused by biological and genetic disorders. His psychiatric theories dominated the field of psychiatry at the beginning of the twentieth century. He vigorously opposed the approach of Freud who regarded and treated psychiatric disorders as caused by mysterious psychological forces. Though Kraepelin's contribution was largely ignored through most of the twentieth century due to an uncritical adoption of the Freudian etiological theories, Kraepelin's basic concepts now dominate psychiatric research and academic psychiatry, and today the published literature in the field of psychiatry is overwhelmingly biological and genetic in its orientation. Largely for political reasons, Kraepelin's great contribution in discovering schizophrenia and manic-depression remains relatively unknown to the general public and his work is little read, despite the recent widespread adoption of his fundamental theories on the etiology and diagnosis of psychiatric disorders which form the basis of all major diagnostic systems in use today, especially the American Psychiatric Association's DSM-IV and the World Health Organization's ICD system.
For a more complete description of the epic social and political battle that gave rise to Freudianism (from an anti-Freudian perspective), see psychiatrist E. Fuller-Torrey's "The Freudian Fraud".
For an extensive bibliography of English translations of Kraepelin's works see: http://www.kraepelin.org/_wsn/page3.html
For an extensive bibliography of works by and about Kraepelin's including those in the original German: http://www.med.uni-muenchen.de/psywifo/Kraepelin.htm
See
For detailed information and replies to questions about Kraepelin contact the International Kraepelin Society: http://www.kraepelin.org/External links
for biographies of Kraepelin.