This group cannot be satisfactorily defined at the present time, as there are still too many points at issue as to what constitute the essential clinical features of dementia praecox. A large majority of the cases which should go into this group may, however, be recognized without special difficulty, although there is an important smaller group of doubtful, atypical, allied or transitional cases which from the standpoint of symptoms or prognosis occupy an uncertain clinical position.

The term "schizophrenia" is now used by many writers instead of dementia praecox. Cases formerly classed as "Allied to Dementia Praecox" should be placed here rather than in the "Undiagnosed" group.

The following mentioned features are sufficiently well established to be considered most characteristic of the dementia praecox type of reaction:

A seclusive type of personality or one showing other evidences of abnormality in the development of the instincts and feelings.

Appearance of defects of interests and discrepancies between thought on the one hand and the behavior-emotional reactions on the other.

A gradual blunting of the emotions, growing indifference or silliness with serious defects of judgment and often hypochondriacal complaints, suspicions or ideas of reference.

Development of peculiar trends, often fantastic ideas, with odd, impulsive or negativistic conduct not accounted for by any acute emotional disturbance or impairment of the sensorium.

Appearance of autistic thinking and dream-like ideas, peculiar feelings of being forced, of interference with the mind, of physical or mystical influences, but with retention of clearness in other fields (orientation, memory, etc.).

According to the prominence of certain symptoms in individual cases the following four clinical forms of dementia praecox may be specified, but it should be borne in mind that these are only relative distinctions and that transitions from one clinical form to another are common:

(a) Paranoid type: Cases characterized by a prominence of delusions, particularly ideas of persecution or grandeur, often connectedly elaborated, with hallucinations in various fields.

(b) Catatonic type: Cases in which there is a prominence of negativistic reactions or various peculiarities of conduct with phases of stupor or excitement, the latter characterized by impulsive, queer or stereotyped behavior and usually hallucinations.

(c) Hebephrenic type: Cases showing prominently a tendency to silliness, smiling and laughing, grimacing, mannerisms in speech and action, and numerous peculiar ideas usually absurd, grotesque and changeable in form.

(d) Simple type: Cases characterized by defects of interest, gradual development of an apathetic state, often with peculiar behavior, but without expression of delusions or hallucinations.