Typical of schizophrenia is the patient’s expression of remarkably unusual experiences and ideas. The patient may express the thought that his body is somehow separated from his mind, that he does not feel like himself, that his body belongs to someone else, or that he is unsure of his own identity or even sex. These experiences have been called depersonalization. Thought insertion, wherein it seems to the patient that an idea has been implanted into his mind, or thought withdrawal, wherein an idea has been extracted from his mind by an outside agency, are other parts of this problem. Closely related, and characteristic of schizophrenia, are ideas of being under the control of some external agency or being made to speak or act in ways that are dictated by others, often through the medium of radar, telepathy, or the Internet (passivity feelings). Thought projection, the notion that external elements in the environment are being controlled by the patient’s mind, is similar. Frequently, there are ideas of reference—that the remarks or actions of others are subtly or overtly directed to the patient. Finally, the patient may feel that the world about him is changed or unnatural, or his perception of time may be altered, not in a brief episode like the jamais vu of a temporal lobe seizure, but continuously; this is the phenomenon of derealization. However, the bizarreness of these delusions, once considered a characteristic feature, has been removed from the diagnostic criteria for schizophrenia in the latest recursion of the DSM (American Psychiatric Association) because of its nonspecificity and the difficulty determining exactly what constitutes bizarre.
Auditory hallucinations are frequent and a core feature of the typical illness. They consist of voices that comment on the patient’s character and activities and are usually accusatory, threatening, or claiming control of the patient’s actions. The voices may or may not be recognized; they may belong to 1 person or 2 or more persons who converse with the patient or with one another. Seldom can the voices be localized to a point outside the patient. Instead, they seem to come from within, so that they cannot be distinguished from his own feelings and thoughts. Certain somatic hallucinations and delusions may predominate in any one individual. Visual, olfactory, and other types of hallucinations also occur but are much less frequent. The patient believes in the reality of these hallucinations and often weaves them into a delusional system.
It should be reiterated here that hallucinations are a feature of a number of neurologic processes, but in most people visual hallucinations predominate, whereas auditory hallucinations are more the hallmark of schizophrenia. Of interest in this regard is “The Report on the Census of Hallucinations” by Sidgwick in 1894 who suggested (as cited by Frith) that almost 1 in 10 ostensibly normal respondents has experienced hallucinations, mostly visual. The main illnesses in which hallucinations and delusions are prominent, for example, hallucinogenic drug ingestion and the Charles Bonnet syndrome (see Chap. 12), have been reviewed by Frith.