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Authors: Perminder S. Sachdev
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1
Introduction
Chapter
3Secondaryhallucinations
Mark Walterfang, Ramon Mocellin, David L. Copolov, and Dennis Velakoulis Facts box
acteristics that distinguish them from related phenomena such as imagery and pseudohallucinations. Slade 1. Infrequent hallucinations – auditory as well and Bentall [2] crystallized these features in their def-as visual – are common in the general inition, proposing that hallucinations are perceptual population and do not necessarily signify a experiences that occur in the absence of appropri-psychiatric disorder.
ate stimuli, have the full force or impact of the cor-2. Hallucinations occur in a number of responding real perception, and are not amenable to psychiatric disorders, and are most common direct and voluntary control. This definition, although in schizophrenia.
widely used, has been subject to suggested amend-3. Hallucinations in the setting of brain disease, ments, for example, by David [3] who defines hallu-that is, of organic etiology, are uncommon in cinations as “sensory experiences which occur in the general practice but are frequently
absence of corresponding external stimulation of the encountered on hospital wards, especially relevant sensory organ, have a sufficient sense of real-among the elderly.
ity to resemble a veridical perception, over which the 4. Although hallucinations may occur in a subject does not feel that he or she has direct and vol-number of modalities within the individual, untary control and which occur in the awake state.”
the etiological, biological, and treatment By providing a less rigid boundary in relation to the facets differ somewhat for auditory, visual, reality-like aspect of the symptom, this definition takes olfactory, gustatory, and tactile
into account the spectrum along which such stimulus-hallucinations.
independent perceptions are described. It also accom-modates the fact that a significant minority of halluci-5. A number of neurological or systemic nators are able to use coping mechanisms to modulate disorders have been associated with
their hallucinations [4] even though they may not feel hallucinations of different modalities.
they can control them.
6. The models of pathogenesis of hallucinations are drawn from a range of different disorders such as delirium, dementia, and
Epidemiology of hallucinations in the
substance-induced states, and bear
community
significant homology to some of the
emergent neurobiology of
In the community, hallucinations most commonly schizophrenia-spectrum disorders.
occur in the absence of psychiatric or neurological disorders. Several major studies have revealed a higher community prevalence of hallucinations than would
Introduction
be expected if they were only reflective of psychiatric The term “hallucination,” which derives from the or neurological disease. Ohayon found that 18% of Greek alyein via the Latin hallucinari, to “wander in a large sample of 13,057 subjects in the nonhospi-the mind” [1], was first used in the English language talized population across three countries – the UK, in 1572 to describe visual phenomena – “ghostes and Germany and Italy – experienced daytime halluci-spirites walking by nyghte” [2]. The essential feature of nations [5] . Among this group, infrequent daytime hallucinations is that they are percepts in the absence hallucinations (less than once a week) occurred in 21
of external stimuli, although they possess other char-16% and frequent hallucinations in 2%. In contrast Introduction – Section 1
to the hallucinations occurring in schizophrenia – in most common – but in comparison to schizophrenia which auditory hallucinations are more common [6] – the hallucinations in that disorder were less severe and among Ohayon’s group of interviewees who halluci-more commonly visual.
nated more than once a week during the daytime, Hallucinations occur in a wide range of disorders, the frequency was greatest in the olfactory
Introduction
Chapter
3Secondaryhallucinations
Mark Walterfang, Ramon Mocellin, David L. Copolov, and Dennis Velakoulis Facts box
acteristics that distinguish them from related phenomena such as imagery and pseudohallucinations. Slade 1. Infrequent hallucinations – auditory as well and Bentall [2] crystallized these features in their def-as visual – are common in the general inition, proposing that hallucinations are perceptual population and do not necessarily signify a experiences that occur in the absence of appropri-psychiatric disorder.
ate stimuli, have the full force or impact of the cor-2. Hallucinations occur in a number of responding real perception, and are not amenable to psychiatric disorders, and are most common direct and voluntary control. This definition, although in schizophrenia.
widely used, has been subject to suggested amend-3. Hallucinations in the setting of brain disease, ments, for example, by David [3] who defines hallu-that is, of organic etiology, are uncommon in cinations as “sensory experiences which occur in the general practice but are frequently
absence of corresponding external stimulation of the encountered on hospital wards, especially relevant sensory organ, have a sufficient sense of real-among the elderly.
ity to resemble a veridical perception, over which the 4. Although hallucinations may occur in a subject does not feel that he or she has direct and vol-number of modalities within the individual, untary control and which occur in the awake state.”
the etiological, biological, and treatment By providing a less rigid boundary in relation to the facets differ somewhat for auditory, visual, reality-like aspect of the symptom, this definition takes olfactory, gustatory, and tactile
into account the spectrum along which such stimulus-hallucinations.
independent perceptions are described. It also accom-modates the fact that a significant minority of halluci-5. A number of neurological or systemic nators are able to use coping mechanisms to modulate disorders have been associated with
their hallucinations [4] even though they may not feel hallucinations of different modalities.
they can control them.
6. The models of pathogenesis of hallucinations are drawn from a range of different disorders such as delirium, dementia, and
Epidemiology of hallucinations in the
substance-induced states, and bear
community
significant homology to some of the
emergent neurobiology of
In the community, hallucinations most commonly schizophrenia-spectrum disorders.
occur in the absence of psychiatric or neurological disorders. Several major studies have revealed a higher community prevalence of hallucinations than would
Introduction
be expected if they were only reflective of psychiatric The term “hallucination,” which derives from the or neurological disease. Ohayon found that 18% of Greek alyein via the Latin hallucinari, to “wander in a large sample of 13,057 subjects in the nonhospi-the mind” [1], was first used in the English language talized population across three countries – the UK, in 1572 to describe visual phenomena – “ghostes and Germany and Italy – experienced daytime halluci-spirites walking by nyghte” [2]. The essential feature of nations [5] . Among this group, infrequent daytime hallucinations is that they are percepts in the absence hallucinations (less than once a week) occurred in 21
of external stimuli, although they possess other char-16% and frequent hallucinations in 2%. In contrast Introduction – Section 1
to the hallucinations occurring in schizophrenia – in most common – but in comparison to schizophrenia which auditory hallucinations are more common [6] – the hallucinations in that disorder were less severe and among Ohayon’s group of interviewees who halluci-more commonly visual.
nated more than once a week during the daytime, Hallucinations occur in a wide range of disorders, the frequency was greatest in the olfactory
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