[11] The ICD-9 simple-type schizophrenia description: A psychosis in which there is insidious development of oddities of conduct, inability to meet the demands of society, and decline in total performance.
Because the schizophrenic symptoms are not clear-cut, diagnosis of this form should be made sparingly, if at all.These are the criteria: Slowly progressive development over a period of at least one year, of all three of the following: (a) A significant and consistent change in the overall quality of some aspects of personal behaviour, manifest as loss of drive and interests, aimlessness, idleness, a self-absorbed attitude and social withdrawal.
(b) Gradual appearance and deepening of negative symptoms such as marked apathy, paucity of speech, underactivity, blunting of affect, passivity and lack of initiative, and poor non-verbal communication.
Absence, at any time, of any symptoms referred to in G1 in F20.0 - F20.3[13] and of hallucinations or well formed delusions of any kind, i.e. the subject must never have met the criteria for any other type of schizophrenia, or any other psychotic disorder.
[3][11][15] Simple-type schizophrenia also appeared in the first two editions of the DSM as an official diagnosis:[11] 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.
The provisional research criteria for it were: Progressive development over a period of at least a year of all of the following: (1) marked decline in occupational or academic functioning (2) gradual appearance and deepening of negative symptoms such as affective flattening, alogia, and avolition (3) poor interpersonal rapport, social isolation or social withdrawal B. Criterion A for Schizophrenia has never been met.
[21] Symptoms identified earlier to dementia simplex are now DSM-attributed by way of improvements in diagnostic technique to other classifications such as neurodegenerative disorders.
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.
[33] However, in an experiment with a small sample size, five patients with a diagnosis of simple deteriorative disorder (DSM-IV) were found to have grey matter deficits, atrophy and reduced cerebral perfusion in the frontal areas.