Source : FISH ’S Clinical psychopathology

Causes

Hallucinations can be the result of intense emotions or psychiatric disorder, suggestion, disorders of sense organs, sensory deprivation and disorders of the central nervous system.

Emotion

Very depressed patients with delusions of guilt may hear voices reproaching them. These are not the continuous voices of paranoid schizophrenia or organic hallucinosis but tend to be disjointed or fragmentary, uttering single words or short phrases such as ‘rotter’, ‘kill yourself’, etc. The occurrence of continuous persistent hallucinatory voices in severe depression should arouse the suspicion of schizophrenia or some intercurrent physical disease.

On the other hand the hallucinations that occur in schizophrenia are often of a persecutory nature and may consist of voices giving a commentary on the person’s actions and discussing him in a hostile manner.

Suggestion

Several experimenters have shown that normal subjects can be persuaded to hallucinate. When asked to walk down a dimly lit corridor and stop when they saw a faint light over the door at the end, most subjects stopped walking at some time during the study saying they could see a light even though none was switched on. Similarly subjects can be persuaded to hallucinate visually or auditorily, either by hypnosis or by brief task-motivating instructions. This latter technique consists in asking the subject to try to hallucinate a tune or an animal and then telling him that much more must be done as most people can hallucinate if they try hard enough. A group in whom suggestion was believed to be relevant to the genesis of hallucinations (Hamilton, 1974) were those with a diagnosis of the so-called ‘hysterical psychosis’. The hallucinations, visual in nature, were said to conform to the patient’s fantasies and cultural background. However, this diagnosis is no longer specifically mentioned, either as a specific category or an inclusion category, in either ICD−10 or DSM−IV and so is only of historical interest. The belief that Ganser syndrome is psychogenic in origin (Ungvari & Mullen, 1997) opens the possibility of the role of suggestion in the genesis of the hallucinations in this condition, although others dispute this and regard it as an organic condition (Latcham et al, 1978). The syndrome is now recognised to occur in a variety of psychiatric disorders, including schizophrenia, dissociative disorder, malingering, organic states, etc.

Disorders of a peripheral sense organ

Hallucinatory voices may occur in ear disease and visual hallucinations in diseases of the eye, but often there is some disorder of the central nervous system as well. For example, a woman aged 66 suffered from glaucoma and then began to have continuous visual hallucinations. At the time she showed evidence of atherosclerotic dementia and had a focus of abnormal activity in the left posterior temporal lobe. Charles Bonnet syndrome (phantom visual images) is a condition in which complex visual hallucinations occur in the absence of any psychopathology and in clear consciousness. It is associated with either central or peripheral reduction in vision and not surprisingly is most common in the elderly but can occur in younger people also.

 The hallucinatory episodes are of variable duration and can last for years. The images may be static or in motion and the importance of this diagnosis is as a differential from psychopathological causes of hallucinations.

Peripheral lesions of sense organs may play a part in hallucinations in organic states and it has been shown that negative scotomota are to be found in patients with alcohol misuse.

Sensory deprivation

If all incoming stimuli are reduced to a minimum in a normal subject, they will begin to hallucinate after a few hours. These hallucinations are usually changing visual hallucinations and repetitive words and phrases. It has been suggested that the sensory isolation produced by deafness may cause paranoid disorders in the deaf (Cooper, 1976). Similarly, sensory deprivation due to the use of protective patches may contribute to the delirium that follows cataract surgery, along with mild cognitive deficits due to ageing.

There is an interesting case on record of a patient who had ‘black patch disease’ after an operation and was frightened by the prospect of another operation on her other eye a few years later. She was reassured by a psychiatrist, who saw her before and immediately afterwards and promised to see her whenever requested during the post-operative period. After the second operation she had no hallucinations of any kind.

Disorders of the central nervous system

Lesions of the diencephalons and the cortex can produce hallucinations that are usually visual but can be auditory.

Hypnagogic and hypnopompic hallucinations are special kinds of organic hallucination