In the preface to the second edition, published in 1919, of his book on general psychopathology, Karl Jaspers wrote: We trail around with us a great number of vague generalities.
I have tried to clarify them as far as possible. But the deep intentions, which sometimes find expression through them, should not simply be set aside and let fall because full clarification has not been attained . . . .
Jaspers did indeed provide illumination at both levels (1946/1963). In order to clarify the key problem of delusion formation he discriminated between phenomena that can be understood in terms of some antecedent factor such as social beliefs or abnormal affects (overvalued and delusion-like ideas), and those that are based on irreducible experiences, not comprehensible in such terms. ‘There is an immediate intrusive knowledge of the meaning and it is this which is itself the delusional experience.’ In the examples he quotes, Jaspers makes it clear that such experiences are direct and sudden in onset, and not congruent with affect.
He and Kurt Schneider kept up a regular correspondence during the years 1921–55 (Janzarik 1984). Schneider (1959, 1976) composed a list of experiences that could, in practice, be used to differentiate schizophrenia from manic-depressive psychosis with reasonable reliability. His ‘first-rank’ symptoms included:
- thoughts experienced as spoken aloud, or echoed, or removed, or broadcast or alien;
- voices heard commenting on the patient’s thoughts or making references in the third person;
- experiencing bodily functions, movements, emotions or will as under the control of some external force or agency;
- delusional atmosphere; and
- delusional perception.
Any of these experiences could be elaborated according to the personal preoccupations of the individual concerned, including those that were socially shared. Schneider did not suggest that the first-rank symptoms carried any special theoretical or prognostic significance but did think (correctly: World Health Organization 1973) that most clinicians would make a diagnosis of schizophrenia if they were present in the absence of evident brain disease.
This still left a small group of seemingly inexplicable delusions that did not fit Schneider’s primary criteria. For example, Kraepelin had regarded paranoia as a separate category. In 1918, Kretschmer (1966/1974) published a monograph on a group of disorders characterized by delusions that developed following a specific stress occurring to someone with a sensitive personality. These conditions could become chronic but were not accompanied by deterioration. Other, usually monothematic delusional disorders have been separated from schizophrenia.
For example, a single delusion that other people think the individual smells, or that some part of the anatomy is distorted or missing, in the absence of any apparent basis in affective, or any other, disorder. One such symptom can ruin the sufferer’s whole life. Acute delusional or hallucinatory states of brief duration, with no subsequent development of schizophrenic symptoms, were classified by French psychiatrists as bouffees delirantes, following Magnan (1893). This rich vein of clinical description facilitated subsequent attempts to operationalize the concepts.