the subject must never have met the criteria for any other type of schizophrenia, or any other psychotic disorder. 3. Absence of evidence of dementia or any other organic mental disorder. The ICD is currently in revision 10, and the ICD-11 was accepted in May 2019 will come into effect in 2022. In the ICD-11, there is no longer a diagnostic category of simple schizophrenia, and all subtypes of schizophrenia have been eliminated. DSM
Simple-type schizophrenia also appeared in the first two editions of the DSM as an official diagnosis:
This psychosis is characterized chiefly by a slow and insidious reduction of external attachments and interests and by apathy and indifference leading to impoverishment of interpersonal relations, mental deterioration, and adjustment on a lower level of functioning. In general, the condition is less dramatically psychotic than are the hebephrenic, catatonic, and paranoid types of schizophrenia. Also, it contrasts with schizoid personality, in which there is little or no progression of the disorder. But after that, it was omitted in later versions and has since then never returned as a formal diagnosis in any DSM. However, DSM-IV (1994) and DSM-IV-TR (2000) included Simple Schizophrenia in the appendix under the proposed category of simple deteriorative disorder.
In 1860, Bénédict Morel introduced the term dementia précoce and Langdon Down provided  in 1887 the most complete description to that date of the clinical manifestation that Charpentier described in 1890 as dementia précoce simple des enfant normaux.The description of simple schizophrenia is inter-changeable with describing symptoms as a form of dementia praecox known as simple dementing, at least in the time when the Swiss psychiatrists Otto Diem and Eugen Bleuler were studying it. In 1893, Emil Kraepelin considered there were four types of schizophrenia, and was amongst the first to identify three of them (dementia hebephrenica, dementia paranoides, dementia catatonica). The simplex type was added by Eugen Bleuler to the earlier ones identified by Kraepelin in 1899 and subsequently given a basic outline in 1903 by Otto Diem publishing a monograph on dementia praecox in the simple dementing form. This was based on a survey of two males having had a relatively normal childhood but who then fell into patterns of living tending towards vagrancy.A description of a cerebral disorder in relation to organic factors and in the context of general paralysis of the insane only; with no reference to schizophrenia, shows a disorder with features of generalized dementia (Lishman 1998). In 1951, a film was made showing the clinical characteristics of simple-type schizophrenia. Controversy
Definition of this type of schizophrenia is without unity or is controversial. The diagnosis was discontinued in the DSM system, although it was recommended for reinclusion in 1989.